In linguistics, wh-movement (also known as wh-fronting, wh-extraction, wh-raising) concerns rules of syntax involving the placement of interrogative words. In plain terms, it refers to an asymmetry between the syntactical arrangement of words or morphemes in a question and the form of answers to that question; specifically, the placement of the question word. An example in English is "What are you doing?", a response to which could be "I am editing Wikipedia."; in which the answer (editing Wikipedia) is at the end of the sentence but the question word (What) is at the beginning.
Interrogative forms, whatever the language, are known within linguistics as wh-words because most question words in the English language start with a wh-; such as what, when, where, who, and why. In English, only one interrogative word does not begin with wh-, namely how. In languages with wh-movement, sentences or clauses with a wh-word show a special word order that places the wh-word (or phrase containing the wh-word) at the front of the sentence or clause (Whom are you thinking about?) instead of the canonical position later in the sentence (I am thinking about you). Leaving the wh-word in its canonical position is called wh-in situ.
Wh-movement often results in a discontinuity, and in that regard, it is one of (at least) four widely acknowledged discontinuity types, the others being topicalization, scrambling, and extraposition. Wh-movement is found in many languages around the world, and of the various discontinuity types, wh-movement is the one that has been studied the most. It is observed in many of the world's languages, and plays a key role theories of long-distance dependencies.
Historically, the name wh-movement stems from early generative grammar (1960s and 1970s) and was a reference to the transformational analysis of the day in which the wh-expression appears in its canonical position at deep structure and then moves leftward from that position to a derived position at the front of the sentence/clause at surface structure. Although many theories of syntax do not use the mechanism of movement in the transformative sense, the term wh-movement (or equivalent terms such as wh-fronting, wh-extraction, wh-raising) is widely used to denote the phenomenon, even in theories that do not model long-distance dependencies as movement.
What needs to be considered is that wh-movement does not occur solely due to interrogative words. Wh-words are used to form questions, and can also occur in relative clauses. Wh-movement occurs from the existing EPP (Extended projection principle). There are three types of wh-expressions overall- Interrogative, Relative, and Pseudo-cleft wh-expressions. 
The following examples of sentence pairs illustrate wh-movement: each (a) example has the canonical word order of a declarative sentence in English; each (b) sentence has undergone wh-movement, whereby the wh-word has been fronted in order to form a question. The relevant words are bolded.
wh-fronting of whom, which corresponds to the direct object Tesnière (1a) Tom has been reading Tesnière. (1b) Whom has Tom been reading?
wh-fronting of what, which corresponds to the prepositional object syntax (2a) She should stop talking about syntax. (2b) What should she stop talking about?
- (3a) They want to visit us tomorrow.
- (3b) When do they want to visit us? (The temporal adjunct corresponding to tomorrow has been wh-fronted as the wh-word when.)
- (4a) She is happy.
- (4b) What is she? (The predicative adjective corresponding to happy has been fronted as the wh-word what.)
- (5a) She is going to school.
- (5b) Where is she going? (The prepositional phrase corresponding to to school has been fronted as the wh-word where.)
- (6a) They are doing well.
- (6b) How are they doing? (The adverb phrase corresponding to well has been fronted as the wh-word how.)
- (7a) She is sad
- (7b) Why is she crying? (The prepositional phrase corresponding to why has been fronted as the wh-word why.)
The examples in (1) through (7) illustrate that wh-fronting occurs when a constituent is questioned that appears to the right of the finite verb in the corresponding declarative sentence. Consider in this regard that when the subject is questioned, there is no obvious reason to assume that wh-fronting has occurred because the default position of the subject is clause-initial:
- a. Fred is working hard.
- b. Who is working hard? – The subject corresponding to Fred already appears at the front of the sentence, so there is no reason to assume that who has been fronted.
Despite the fact that such data provide no obvious reason to assume movement, some theories of syntax maintain a movement analysis in the interest of remaining consistent. They assume that the wh-subject has in fact moved up the syntactic hierarchy, although this movement is not apparent from the actual linear order of the words.
Wh-movement occurs in ex situ forms, where the structure moves from the base to the Spec C with the help of EPP.
Each one of the Wh-words is responsible for a certain description or target.
- Locative-> Where
- Temporal-> When
- Object-> Who, What
- Manner-> How
- Rationale-> Why, What
Wh-expressions without wh-movementEdit
Wh-movement typically occurs to form questions in English. There are, however, at least three kinds of questions in which wh-movement does not occur (aside from when the question word serves as the subject and so is already fronted):
- Echo questions: (to confirm what you thought you heard)
- Quiz questions or specific questions: ask for detailed specific information that the individual has encountered before
- Multiple questions in a single sentence:when there is already one wh-word at the front:
- Expected questions: Occur when new information is expected 
- Reference questions: Asking for someone to repeat what already has been said/ paraphrasing 
- You bought what!? – Echo question
- George Orwell was born in which country? – Quiz question
- Who bought what? – Multiple wh-expressions
While wh-movement is the rule (and these three cases are the exceptions to the rule) in English, other languages may leave wh-expressions in situ (in base position) more often such as in Slavic Languages . In French for instance, wh-movement is often optional in certain matrix clauses.
The EPP (Extended projection principle) plays a great role in the case of wh-movement. For those languages that leave wh-expressions in situ, we may see a pattern in that EPP does not exist in the structure itself- unlike ex situ where movement is allowed and the EPP is present.
Some example of languages that possess Wh-expressions without wh-movement (are in situ) are Chinese and Slavic languages- languages that are most commonly used as examples are Mandarin and Russian.
It also needs to be considered that in situ questions are different from wh-fronted questions as they follow two different paths:
1) Typically, in situ expressions result from no movement at all which tends to be morphologically or pragmatically conditioned 
2) Wh-expressions/words are always moved 
In subordinate clausesEdit
The examples in the previous section have wh-movement occurring in main clauses (in order to form a question). Wh-movement is not restricted to occurring in main clauses. It frequently appears in subordinate clauses, although its behavior in subordinate clauses differs in a key respect, viz. word order. The following two subsections consider wh-movement in indirect questions and relative clauses.
In indirect questionsEdit
In English, wh-movement occurs to form a question in both main and subordinate clauses. When the question is expressed with a main clause, it is a direct question. When the question is expressed with a subordinate clause, however, it is an indirect question. While wh-fronting occurs in both direct and indirect questions, there is a key word order difference that distinguishes between the two. This difference is illustrated with the following data:
- a. Fred will ask Jill to leave.
- b. Whom1 will2 Fred ask to leave? – Direct question
- c. I wonder whom1 Fred2 will3 ask to leave. – Indirect question
- a. Sam likes to get news about hurricanes.
- b. What1 does2 Sam like to get news about? – Direct question; do-support introduced
- c. They asked what1 Sam2 likes3 to get news about. – Indirect question
- a. Larry stayed home due to the weather.
- b. Why1 did2 Larry stay home? – Direct question; do-support introduced
- c. Nobody knows why1 Larry2 stayed3 home. – Indirect question
The subscripts indicate a central word order difference across direct and indirect questions. Wh-fronting in main clauses typically results in V2 word order in English, meaning the finite verb appears in second position, as marked by the 2-subscript in the b-sentences. In indirect questions, however, V3 word order typically obtains, as marked by the 3-subscript in the c-sentences. Despite this systematic word order difference across direct and indirect questions, wh-fronting within the clause is occurring in both cases. Note as well that do-support is often needed in order to enable wh-fronting. Wh-fronting in main clauses is often reliant on subject–auxiliary inversion.
In relative clausesEdit
The examples above all involve interrogative clauses (questions). Wh-movement also occurs in relative clauses, however, which cannot be interpreted as questions. Many relative pronouns in English have the same form as the corresponding interrogative words (which, who, where, etc.). Relative clauses are subordinate clauses, so the characteristic V3 word order seen in indirect questions occurs:
- a. I read Fred's paper.
- b. Fred's paper, which1 I2 read3 – Wh-fronting in relative clause
- c. *Fred's paper, which1 did2 I read – Wh-fronting impossible with V2 word order in subordinate clause
- a. John likes the governor.
- b. the governor whom1 John2 likes3 – Wh-fronting in relative clause
- c. *the governor whom1 does2 John like – Wh-fronting impossible with V2 word order in subordinate clause
- a. Fred reads the paper in the coffee shop.
- b. the coffee shop where1 Fred2 reads3 the paper – Wh-fronting in relative clause
- c. *the coffee shop where1 does2 Fred read the paper – Wh-fronting impossible in subordinate clause with V2 word order
The relative pronouns have fronted in the subordinate clauses of the b-examples, just like they are fronted in the indirect questions in the previous sections. The characteristic V3 word order is obligatory. If the V2 word of main clauses occurs, the sentence is bad, as the c-examples demonstrate.
Many instances of wh-fronting involve pied-piping. Pied-piping occurs when a fronted wh-word (or otherwise focused word) pulls an entire encompassing phrase to the front of the clause with it, i.e. it "pied-pipes" the other words of the phrase with it to the front of the clause (see the Pied Piper of Hamelin). The following two subsections consider both obligatory and optional pied-piping.
Pied-piping is sometimes obligatory. That is, in order for a wh-expression to be fronted, an entire encompassing phrase must be fronted with it. The relevant phrase of pied-piping is underlined in the following examples:
- a. Susan is reading Fred's novel.
- b. Whose novel is Susan reading? – Pied-piping of novel
- c. *Whose is Susan reading novel? – Sentence is bad because pied-piping has not occurred.
- a. The music is very loud.
- b. How loud is the music? – Pied-piping of loud
- c. *How is the music loud? – Sentence is bad because pied-piping has not occurred.
These examples illustrate that pied-piping is often necessary when the wh-word is inside a noun phrase (NP) or adjective phrase (AP). Pied-piping is motivated in part by the barriers and islands to extraction (see below). When the wh-word appears underneath a blocking category or in an island, the entire encompassing phrase must be fronted. Pied-piping was first identified by John R. Ross in his 1967 dissertation.
There are cases where pied-piping can be optional. In English, this occurs most notably with prepositional phrases (PPs). The wh-word is the object of a preposition. A formal register will pied-pipe the preposition, whereas more colloquial English prefers to leave the preposition in situ, e.g.
- a. She revealed her secret to Tom.
- b. To whom did she reveal her secret? – Pied-piping of preposition associated with a formal register
- c. Whom did she reveal her secret to? – Pied-piping absent in colloquial, everyday English
- a. He is hiding behind the red door.
- b. Behind which door is he hiding? – Pied-piping of preposition associated with a formal register.
- c. Which door is he hiding behind? – Pied-piping absent in colloquial, everyday English
The c-examples are cases of preposition stranding, which is possible in English, but not allowed in many languages that are related to English. For instance, preposition stranding is largely absent from many of the other Germanic languages and it may be completely absent from the Romance languages. Prescriptive grammars often claim that preposition stranding should be avoided in English as well; however, in certain contexts pied-piping of prepositions in English may make a sentence feel artificial or stilted.
In many cases, a Wh-expression can occur at the front of a sentence regardless of how far away its canonical location is, e.g.
- a. Whom does Mary like __?
- b. Whom does Bob know that Mary likes __?
- c. Whom does Carl believe that Bob knows that Mary likes __?
The Wh-word whom is the direct object of the verb likes in each of these sentences. There appears to be no limit on the distance that can separate the fronted expression from its canonical position. In more technical terms, we can say that the dependency relation between the gap (the canonical, empty position) and its filler (the Wh-expression) is unbounded in the sense that there is no upper bound on how deeply embedded within the given sentence the gap may appear.
However, there are cases in which this is not possible. Certain kinds of phrases do not seem to allow a gap. The phrases from which a Wh-word cannot be extracted are referred to as extraction islands or simply islands. The following subsections briefly consider seven types of islands: 1) adjunct islands, 2) Wh-islands, 3) subject islands, 4) left branch islands, 5) coordinate structure islands, 6) complex NP islands, and 7) non-bridge islands. These island types were all originally identified in Ross' seminal dissertation. The islands in the examples that follow are underlined in the a-sentences.
An adjunct island is a type of island formed from an adjunct clause. Wh-movement is not possible out of an adjunct clause. Adjunct clauses include clauses introduced by because, if, and when, as well as relative clauses. Some examples include:
- a. You went home because you needed to do that?
- b. *What did you go home because you needed to do __? – The attempt to extract out of an adjunct clause fails.
- a. Alex likes the woman who wears tight sweaters?
- b. *What does Alex like the woman who wears __? – The attempt to extract out of an adjunct clause fails.
Wh-movement fails in the b-sentences because the gap appears in an adjunct clause.
A wh-island is created by an embedded sentence which is introduced by a Wh-word. Wh-islands are weaker than adjunct islands and violating them results in the sentence sounding ungrammatical to the native speaker.
- a. John wonders where Eric went to buy a gift?
- b. ??What does John wonder where Eric went to buy __? – The attempt to extract out of a wh-island is at best strongly marginal.
- a. Susan asked why Sam was waiting for Fred.
- b. *Whom did Susan ask why Sam was waiting for __? – The attempt to extract out of a wh-island fails.
The b-sentences are strongly marginal/unacceptable because one has attempted to extract an expression out of a wh-island.
The reason why this occurs is because both wh-words are part of a DP. It would not be possible to move the bottom wh-word to the top of the structure, as they would both interfere. In order to get a grammatical result, a proper wh-movement must occur. However, because the wh-word is taking up the Spec- C position, it is not possible to move the competing wh-word higher by skipping the higher DP as wh-movement is a cyclic process.
Wh-movement is not (or hardly) possible out of subjects, at least not in English. This is particularly true for subject clauses, and to a somewhat lesser extent out of subject phrases, e.g.
- a. That John went home is likely.
- b. *Who is that __ went home likely? – Wh-extraction out of a subject clause fails.
- a. The story about Susan was funny.
- b. ??Whom was the story about __ funny? – Wh-extraction out of subject phrase is strongly marginal.
The important insight here is that wh-extraction out of object clauses and phrases is quite possible. There is therefore an asymmetry across subjects and objects with respect to wh-movement.
Left branch islandsEdit
Modifiers that would appear on a left branch under a noun (i.e. they precede the noun that they modify) cannot be extracted. The relevant constraint is known as the Left Branch Condition, and Ross (1967) is again credited with having discovered it. The left branch constraint captures the fact that possessive determiners and attributive adjectives in English and many related languages necessarily pied-pipe the entire noun phrase when they are fronted, e.g.
- a. Susan likes Fred's account.
- b. *Whose does Susan like __ account? – Attempt to extract from a left branch under a noun fails.
- c. Whose account does Susan like __? – Extraction succeeds if the entire NP is pied piped.
- a. He bought an expensive boat.
- b. *How expensive did he buy a __ boat? – Attempt to extract from a left branch under a noun fails.
- c. How expensive a boat did he buy? – Extraction succeeds if the entire NP is pied piped.
Extraction fails in the b-sentences because the extracted expression corresponds to a left-branch modifier of a noun. Left branch islands are cross-linguistically variable. While they exist in English, they are absent from many other languages, most notably, from the Slavic languages.
Coordinate structure islandsEdit
In coordination, extraction out of a conjunct of a coordinate structure is possible only if this extraction affects all the conjuncts of the coordinate structure equally. The relevant constraint is known as the coordinate structure constraint. Extraction must extract the same syntactic expression out of each of the conjuncts simultaneously. This sort of extraction is said to occur across the board (ATB-extraction), e.g.
- a. Sam ate [beans] and [broccoli].
- b. *What did Sam eat [beans] and [__]? – Extraction fails because it affects just one conjunct.
- a. Sam ate [beans] and [broccoli].
- b. *What did Sam eat [__] and [broccoli]? – Extraction fails because it affects just one conjunct.
- a. Sam [gave a guitar to me] and [loaned a trumpet to you].
- b. What did Sam [give __ to me] and [loan __ to you]? – Extraction succeeds because it occurs equally out of both conjuncts (ATB-extraction).
- a. He is [waiting for you] and [trying to call you].
- b. Whom is he [waiting for __] and [trying to call __]? – Extraction succeeds because it occurs equally out off both conjuncts (ATB-extraction).
Wh-extraction out of a conjunct of a coordinate structure is only possible if it can be interpreted as occurring equally out all the conjuncts simultaneously, that is, if it occurs across the board.
Complex noun phrase islandsEdit
Extraction is difficult from out of a noun phrase. The relevant constraint is known as the complex NP constraint, and comes in two varieties, the first banning extraction from the clausal complement of a noun, and the second banning extraction from a relative clause modifying a noun:
Sentential complement to a noun:
- a. You heard the claim that Fred solved the second problem.
- b. ??What did you hear the claim that Fred solved __? – Attempt to extract out of a complex NP fails.
- a. She likes the possibility that she might get a new phone for X-mas.
- b. ??What does she like the possibility that she might get __ for X-mas? – Attempt to extract out of a complex NP fails.
- a. They hired someone who speaks a Balkan language.
- b. *What Balkan language did they hire someone who speaks __?
Extraction out of object that-clauses serving as complements to verbs may show island-like behavior if the matrix verb is a non-bridge verb (Erteschik-Shir 1973). Non-bridge verbs include manner-of-speaking verbs, such as whisper or shout, e.g.
- a. She thinks that he died in his sleep.
- b. How does she think that he died __? – Extraction out of object clause easily possible with matrix bridge verb.
- a. She whispered that he had died in his sleep.
- b. *How did she whisper that he had died __? – Extraction across a non-bridge verb is impossible.
Wh-Movement in Syntax TreesEdit
Syntax trees are visual breakdowns of sentences that include dominating heads for every segment (word/constituent) in the tree itself. In the Wh-Movement, there are additional segments that are added- EPP ( Extended projection principle ) and the Question Feature [+Q] that represents a question sentence.
The Wh-movement is motivated by a Question Feature/EPP at C (Complementizer), which promotes movement of a Wh-word from the canonical base position to Spec-C. This movement could be considered as “Copy + Paste + Delete” movement as we are copying the interrogative word from the bottom, pasting it to Spec-C, and then deleting it from the bottom so that it solely remains at the top (now taking the position of Spec-C). Overall, the highest C will be the target position of the Wh-Raising. 
The interrogatives that are used in the Wh-Movement do not all share headedness. This is important to consider when making the syntax trees, as there are three different heads that may be used
Determiner Phrase (DP): Who, What
Prepositional Phrase (PP): Where, When, Why
Adverb Phrase (AdvP): How
When creating the Syntax Tree for the Wh-movement, consider the subject-aux inversion in the word that was raised from T (Tense) to C (Complementizer).
The location of the EPP (Extended Projection Principle):
The EPP allows movement of the Wh-word from the bottom canonical position of the syntax tree to Spec C. The EPP is a great indicator when it comes to distinguishing between in-situ trees and ex-situ. Ex situ trees allow the movement to Spec C, while in situ do not as the head C lacks the EPP feature.
Islands in Syntax Trees:
Within Syntax trees, islands do not allow movement to occur- if movement is attempted, the sentence would then be perceived as ungrammatical to the native speaker of the observed language. Islands are typically noted as being a boxed node on the tree. The movement in the Wh-Island syntax tree is unable to occur because in order to move out of an embedded clause, a Determiner Phrase (DP) must move through the Spec C position. This cannot occur, as the Determiner Phrase (DP) is already occupied.
“She said [who bought what]?”. We see that “who” takes the place of DP and restricts “what” from rising up to the respected Spec C. Native speakers may confirm this as well as it will sound ungrammatical * ”What did she say [bought what?]”.
In other languagesEdit
Wh-movement is also found in many other languages around the world. Most European languages also place wh-words at the beginning of a clause. Furthermore, many of the facts illustrated above are also valid for other languages. The systematic difference in word order across main wh-clauses and subordinate wh-clauses shows up in other languages in varying forms. The islands to wh-extraction are also present in other languages, but there will be some variation. The following example illustrates wh-movement of an object in Spanish:
a. Juan compró carne. John bought meat. 'John bought meat.' b. ¿Qué compró Juan? what bought John 'What did John buy?'
The following examples illustrates wh-movement of an object in German:
a. Er liest Tesnière jeden Abend. He reads Tesnière every evening. 'He reads Tesnière every evening.' b. Wen liest er jeden Abend? who reads he every evening 'Who does he read every evening?'
The following examples illustrate wh-movement an object in French:
a. Ils ont vu Pierre. they have seen Peter 'They saw Peter.' b. Qui est-ce qu' ils ont vu? Who is it that they have seen 'Who did they see?' c. Qui ont ils vu? Who have they seen 'Who did they see?'
All the examples are quite similar to the English examples and demonstrate that wh-movement is a general phenomenon in numerous languages. As stated however, the behavior of wh-movement can vary, depending on the individual language in question.
Languages in which it is not presentEdit
Many languages do not have wh-movement. Instead, these languages keep the symmetry of the question and answer sentences.
For example, topic questions in Chinese have the same sentence structure as their answers:
- Literal: You (PROG) do what?
- Translation: What are you doing?
The response to which could be:
- Literal: I (PROG) edit Wikipedia.
- Translation: I am editing Wikipedia.
It needs to be considered that Chinese in fact have a wh-particle. However, there is no wh-movement.
The Russian language tends to maintain the symmetry of their wh-sentences.
anʝ uvidɛlɐ kɐvɔ
Аня увидела кого?
- Literal: Anna saw who?
- Translation: Anna saw who?
The response to which could be:
anʝ uvidɛlɐ ɐlisu
Аня увидела Алису
- Literal: Anna saw Alice
- Translation: Anna saw Alice
An additional example in Ukrainian:
tiperʂɘ cɐs ti dɛ?
теперішній час ти де?
- Literal: this hour you where?
- Translation: Where are you right now?
The response to which could be:
tiperʂɘ cɐs ʝ vdomɐ
теперішній час я вдома
- Literal: this hour i'm home
- Translation: I'm home right now
With respect to Russian and Ukrainian, we may also say these exact sentences with the wh-word fronted. However, these sentences will still be symmetrical even considering that we have changed the position of the wh-word.
Russian example considering the examples above:
кого увидела Аня?
Алису увидела Аня.
Ukrainian example considering the examples above:
де ти теперішній час?
вдома я теперішній час.
Superiority plays a large role in in situ expressions. Superiority means that free order of wh-constituents is occurring within the sentence that is presented . This lack of superiority obtains even where the question feature is present and is why wh-words are still able to be fronted without movement as we see in the examples of Russian and Ukrainian above. Wh-fronting may not always be solely there for the purpose of a question, but rather for reasons of focus feature .
Wh-movement typically results in a discontinuity: the "moved" constituent ends up in a position that is separated from its canonical position by material that syntactically dominates the canonical position, which means there seems to be a discontinuous constituent and a long distance dependency present. Such discontinuities challenge any theory of syntax, and any theory of syntax is going to have a component that can address these discontinuities. In this regard, theories of syntax tend to explain discontinuities in one of two ways, either via movement or via feature passing. The EPP feature (Extended projection principle) and Question Feature play a large role in the movement itself. We have noticed that these two features occur in ex situ questions which allow movement and do not exist in in situ questions that do allow it.
Theories that posit movement have a long and established tradition that reaches back to early Generative Grammar (1960s and 1970s). They assume that the displaced constituent (e.g. the wh-expression) is first generated in its canonical position at some level or point in the structure generating process below the surface. This expression is then moved or copied out of this base position and placed in its surface position where it actually appears in speech. Movement is indicated in tree structures using one of a variety of means (e.g. a trace t, movement arrows, strikeouts, lighter font shade, etc.).
The alternative to the movement approach to wh-movement and discontinuities in general is feature passing. This approach rejects the notion that movement in any sense has occurred. The wh-expression is base generated in its surface position, and instead of movement, information passing (i.e. feature passing) occurs up or down the syntactic hierarchy to and from the position of the gap.
- Accounts of wh-fronting appear in many textbooks on syntax and grammar, e.g. Stockwell (1977:35ff.), Baker (1978:119ff.), Riemsdijk and Williams (1986:19ff.), Borsley (1988:188ff.), Radford (1997:267ff.), Roberts (1999:35ff.), Tallerman (2005:217ff.), Carnie (2013:357ff.).
- For early accounts of question formation and wh-movement, see, for instance, Ross (1967/86:18ff.), Bach (1974:129), Culicover (1976:73f.), Stockwell (1977:172f.), Baker (1978:121f.).
- Wetzels, Leo; Menuzzi, Sergio; Costa, João (eds.). The handbook of Portuguese linguistics (1 ed.). Malden, MA. ISBN 9781118791745. OCLC 944246651.
- Stepanov, Arthur. Wh-scope marking in Slavic. OCLC 449924033.
- Concerning wh-movement in French, see Bošković (2002).
- Concerning the key word order difference across direct and indirect questions, see for instance Roberts (1997:37) and Groß and Osborne (2009:74ff.), and Carnie (2013:367).
- See Carnie (2013:369ff.) for an analysis of relative clauses in terms of wh-movement.
- See Ross' (1967/86:121ff.) original account of pied-piping. For further analyses of pied-piping, see for instance Riemsdijk and Williams (1986:28ff.) and Radford (1997:276ff).
- Concerning preposition stranding in wh-questions in English, see Roberts (1997:212f) and Radford (1999:278ff.).
- For general accounts of island phenomena, see for instance Riemsdijk and Williams (1986:23ff), Roberts (1997:186ff.), Borsley (1999:205ff.), and Carnie (2013:374ff.).
- Concerning subject islands, see Ross (1967/86:148f.), Culicover (1976:282ff.), Borsley (1999:206), Radford (1997:281).
- Ross (1967/86) gives his left branch condition on page 127: "No NP which is the leftmost constituent of a larger NP can be reordered out of this NP by a transformational rule".
- Concerning the lack of left branch islands in Slavic languages, see Ross (1967/86:145), Grosu (1973), Roberts (1997:189).
- Concerning the coordinate structure constraint, see Ross (1967/86:97ff.), Bach (1974:210), Culicover (1976:281ff.), Roberts (1997:188).
- The term across the board is from Williams (1978). See also Roberts (1997:188), Borsley (1999:207).
- Concerning the complex NP constraint, see for instance Ross (1967/86:272ff.), Culicover (1976:280f.), Baker (1978:200ff.), Borsley (1999:206f.)
- For an example of the movement/copying approach, see Radford (2004:153ff.).
- Bach, E. 1974. Syntactic theory. New York: Holt, Rinehart and Winston, Inc.
- Baker, C. 1978. Introduction to generative-transformational syntax. Englewood Cliffs, NJ: Prentice-Hall.
- Borsley, R. 1999. Syntactic theory: A unified approach. London: Arnold.
- Bošković 2002. On multiple wh-fronting. Linguistic Inquiry 33, 351-384.
- Carnie, A. Syntax: A generative introduction. Malden, MA: Wiley-Blackwell.
- Chomsky, N. 1977. On wh-movement. In Culicover, P. W., Wasow, Thomas, and Akmajian, Adrian (eds), Formal Syntax, New York.
- Costa, J et al. 2016. The Handbook of Portuguese Linguistics. (2016). The Handbook of Portuguese Linguistics, pp.288-302.
- Culicover, P. 1976. Syntax. New York: Academic Press.
- David Crystal (23 September 2011). A Dictionary of Linguistics and Phonetics. John Wiley & Sons. ISBN 978-1-4443-5675-5.
- Erteschik-Shir, N. 1973. On the nature of island constraints. Ph. D. thesis, Massachusetts Institute of Technology, Cambridge, MA.
- Groß, T. and T. Osborne 2009. Toward a practical dependency grammar theory of discontinuities. SKY Journal of Linguistics 22, 43-90.
- Jurafsky, D. and J. Martin. 2008. Speech and language processing: An introduction to natural language processing, computational linguistics, and speech recognition. Delhi, India: Pearson Education.
- Grosu, A. 1973. On the Left Branch Condition. Linguistic Inquiry.
- O'Grady, W. 2005. Syntactic carpentry: An emergentist approach. Mahwah, NJ: Lawrence Erlbaum Associates, Publishers.
- Parra-Guinaldo, V. 2013. A generativist approach to renewal in the left periphery: The reanalysis of ‘whether’. Saarbrücken: Lambert.
- Radford, A. 2004. English syntax: An introduction. Cambridge, UK: Cambridge University Press.
- Riemsdijk, H. van and E. Williams. 1986. Introduction to the theory of grammar. Cambridge, MA: The MIT Press.
- Roberts, I. 1997. Comparative syntax. London: Arnold.
- Ross, J. 1967. Constraints on variables in syntax. Doctoral dissertation, Massachusetts Institute of Technology.
- Ross, J. 1986. Infinite syntax. (Originally presented as the author's thesis from 1967). Norwood, NJ: Infinite syntax!
- Stockwell, R. 1977. Foundations of syntactic theory. Englewood Cliffs, NJ: Prentice-Hall, Inc.
- Tallerman, M. 2005. Understanding syntax. 2nd edition. Malta: Hodder Arnold.
- Williams, E. 1978. Across the board rule application. Linguistic Inquiry 9, 31-43.
- Lexicon of Linguistics:Wh-movement
- Lexicon of Linguistics:Pied piping
- Lexicon of Linguistics:Island
- Lexicon of Linguistics:Wh-island
- Lexicon of Linguistics:Left Branch Condition
- Lexicon of Linguistics:Wh-in-situ
- Stanford Linguistics 222B: Foundations of Syntactic Theory II Filler-Gap Dependencies (Unbounded Dependency Constructions) has a good archive of essential papers in the field