A tool is an object that can extend an individual's ability to modify features of the surrounding environment or help them accomplish a particular task. Although many animals use simple tools, only human beings, whose use of stone tools dates back hundreds of millennia, have been observed using tools to make other tools.

Carpentry tools recovered from the wreck of a 16th-century sailing ship, the Mary Rose. From the top, a mallet, brace, plane, handle of a T-auger, handle of a gimlet, possible handle of a hammer, and rule.

Early human tools, made of such materials as stone, bone, and wood, were used for the preparation of food, hunting, the manufacture of weapons, and the working of materials to produce clothing and useful artifacts and crafts such as pottery, along with the construction of housing, businesses, infrastructure, and transportation. The development of metalworking made additional types of tools possible. Harnessing energy sources, such as animal power, wind, or steam, allowed increasingly complex tools to produce an even larger range of items, with the Industrial Revolution marking an inflection point in the use of tools. The introduction of widespread automation in the 19th and 20th centuries allowed tools to operate with minimal human supervision, further increasing the productivity of human labor.

By extension, concepts that support systematic or investigative thought are often referred to as "tools" or "toolkits".



While a common-sense understanding of the meaning of tool is widespread, several formal definitions have been proposed.

In 1981, Benjamin Beck published a widely used definition of tool use.[1] This has been modified to:

The external employment of an unattached or manipulable attached environmental object to alter more efficiently the form, position, or condition of another object, another organism, or the user itself, when the user holds and directly manipulates the tool during or prior to use and is responsible for the proper and effective orientation of the tool.[2]

Other, briefer definitions have been proposed:

An object carried or maintained for future use.

— Finn, Tregenza, and Norman, 2009.[3]

The use of physical objects other than the animal's own body or appendages as a means to extend the physical influence realized by the animal.

— Jones and Kamil, 1973[4]

An object that has been modified to fit a purpose ... [or] An inanimate object that one uses or modifies in some way to cause a change in the environment, thereby facilitating one's achievement of a target goal.

— Hauser, 2000[5]


Prehistoric stone tools over 10,000 years old, found in Les Combarelles cave, France
An upholstery regulator

Anthropologists believe that the use of tools was an important step in the evolution of mankind.[6] Because tools are used extensively by both humans (Homo sapiens) and wild chimpanzees, it is widely assumed that the first routine use of tools took place prior to the divergence between the two ape species.[7] These early tools, however, were likely made of perishable materials such as sticks, or consisted of unmodified stones that cannot be distinguished from other stones as tools.

Stone artifacts date back to about 2.5 million years ago.[8] However, a 2010 study suggests the hominin species Australopithecus afarensis ate meat by carving animal carcasses with stone implements. This finding pushes back the earliest known use of stone tools among hominins to about 3.4 million years ago.[9] Finds of actual tools date back at least 2.6 million years in Ethiopia.[10] One of the earliest distinguishable stone tool forms is the hand axe.

Up until recently, weapons found in digs were the only tools of "early man" that were studied and given importance. Now, more tools are recognized as culturally and historically relevant. As well as hunting, other activities required tools such as preparing food, "...nutting, leatherworking, grain harvesting and woodworking..."[11] Included in this group are "flake stone tools".

Tools are the most important items that the ancient humans used to climb to the top of the food chain; by inventing tools, they were able to accomplish tasks that human bodies could not, such as using a spear or bow to kill prey, since their teeth were not sharp enough to pierce many animals' skins. "Man the hunter" as the catalyst for Hominin change has been questioned. Based on marks on the bones at archaeological sites, it is now more evident that pre-humans were scavenging off of other predators' carcasses rather than killing their own food.[12]

Timeline of ancient tool development


Many tools were made in prehistory or in the early centuries of recorded history, but archaeological evidence can provide dates of development and use.[13][14][15]

Several of the six classic simple machines (wheel and axle, lever, pulley, inclined plane, wedge, and screw) were invented in Mesopotamia.[16] The wheel and axle mechanism first appeared with the potter's wheel, invented in what is now Iraq during the 5th millennium BC.[17] This led to the invention of the wheeled vehicle in Mesopotamia during the early 4th millennium BC.[18] The lever was used in the shadoof water-lifting device, the first crane machine, which appeared in Mesopotamia c. 3000 BC,[19] and then in ancient Egyptian technology c. 2000 BC.[20] The earliest evidence of pulleys date back to Mesopotamia in the early 2nd millennium BC.[21]

The screw, the last of the simple machines to be invented,[22] first appeared in Mesopotamia during the Neo-Assyrian period (911–609 BC).[21] The Assyrian King Sennacherib (704–681 BC) claims to have invented automatic sluices and to have been the first to use water screw pumps, of up to 30 tons weight, which were cast using two-part clay molds rather than by the 'lost wax' process.[23] The Jerwan Aqueduct (c. 688 BC) is made with stone arches and lined with waterproof concrete.[24] The earliest evidence of water wheels and watermills date back to the ancient Near East in the 4th century BC,[25] specifically in the Persian Empire before 350 BC, in the regions of Mesopotamia (Iraq) and Persia (Iran).[26] This pioneering use of water power constituted perhaps the first use of mechanical energy.[27]

Mechanical devices experienced a major expansion in their use in Ancient Greece and Ancient Rome with the systematic employment of new energy sources, especially waterwheels. Their use expanded through the Dark Ages with the addition of windmills.

Machine tools


Machine tools occasioned a surge in producing new tools in the Industrial Revolution. Pre-industrial machinery was built by various craftsmen—millwrights built water and windmills, carpenters made wooden framing, and smiths and turners made metal parts. Wooden components had the disadvantage of changing dimensions with temperature and humidity, and the various joints tended to rack (work loose) over time. As the Industrial Revolution progressed, machines with metal parts and frames became more common.[28][29]

Other important uses of metal parts were in firearms and threaded fasteners, such as machine screws, bolts, and nuts. There was also the need for precision in making parts. Precision would allow better working machinery, interchangeability of parts, and standardization of threaded fasteners. The demand for metal parts led to the development of several machine tools. They have their origins in the tools developed in the 18th century by makers of clocks and watches and scientific instrument makers to enable them to batch-produce small mechanisms. Before the advent of machine tools, metal was worked manually using the basic hand tools of hammers, files, scrapers, saws, and chisels. Consequently, the use of metal machine parts was kept to a minimum. Hand methods of production were very laborious and costly and precision was difficult to achieve.[30][31] With their inherent precision, machine tools enabled the economical production of interchangeable parts.[28][29][32]

Examples of machine tools include:[28][29]

Advocates of nanotechnology expect a similar surge as tools become microscopic in size.[33][34]



One can classify tools according to their basic functions:

Some tools may be combinations of other tools. An alarm-clock is for example a combination of a measuring tool (the clock) and a perception tool (the alarm). This enables the alarm-clock to be a tool that falls outside of all the categories mentioned above.

There is some debate on whether to consider protective gear items as tools, because they do not directly help perform work, just protect the worker like ordinary clothing. They do meet the general definition of tools and in many cases are necessary for the completion of the work. Personal protective equipment includes such items as gloves, safety glasses, ear defenders and biohazard suits.[38]



Tool substitution


Often, by design or coincidence, a tool may share key functional attributes with one or more other tools. In this case, some tools can substitute for other tools, either as a makeshift solution or as a matter of practical efficiency. "One tool does it all" is a motto of some importance for workers who cannot practically carry every specialized tool to the location of every work task, such as a carpenter who does not necessarily work in a shop all day and needs to do jobs in a customer's house. Tool substitution may be divided broadly into two classes: substitution "by-design", or "multi-purpose", and substitution as makeshift. Substitution "by-design" would be tools that are designed specifically to accomplish multiple tasks using only that one tool.

Substitution is "makeshift" when human ingenuity comes into play and a tool is used for an unintended purpose, such as using a long screwdriver to separate a cars control arm from a ball joint, instead of using a tuning fork. In many cases, the designed secondary functions of tools are not widely known. For example, many wood-cutting hand saws integrate a square by incorporating a specially-shaped handle, that allows 90° and 45° angles to be marked by aligning the appropriate part of the handle with an edge, and scribing along the back edge of the saw. The latter is illustrated by the saying "All tools can be used as hammers". Nearly all tools can be used to function as a hammer,[39] even though few tools are intentionally designed for it and even fewer work as well as the original.

Bicycle multi-tool

Tools are often used to substitute for many mechanical apparatuses, especially in older mechanical devices. In many cases a cheap tool could be used to occupy the place of a missing mechanical part. A window roller in a car could be replaced with pliers. A transmission shifter or ignition switch would be able to be replaced with a screwdriver. Again, these would be considered tools that are being used for their unintended purposes, substitution as makeshift. Tools such as a rotary tool would be considered the substitution "by-design", or "multi-purpose". This class of tools allows the use of one tool that has at least two different capabilities. "Multi-purpose" tools are basically multiple tools in one device/tool. Tools such as this are often power tools that come with many different attachments like a rotary tool does, so one could say that a power drill is a "multi-purpose" tool.[40]

Multi-use tools


A multi-tool is a hand tool that incorporates several tools into a single, portable device; the Swiss Army knife represents one of the earliest examples.[41] Other tools have a primary purpose but also incorporate other functionality – for example, lineman's pliers incorporate a gripper and cutter and are often used as a hammer;[39] and some hand saws incorporate a square in the right-angle between the blade's dull edge and the saw's handle. This would also be the category of "multi-purpose" tools, since they are also multiple tools in one (multi-use and multi-purpose can be used interchangeably – compare hand axe). These types of tools were specifically made to catch the eye of many different craftsman who traveled to do their work. To these workers these types of tools were revolutionary because they were one tool or one device that could do several different things. With this new revolution of tools, the traveling craftsman would not have to carry so many tools with them to job sites, in that their space would be limited to the vehicle or to the beast of burden they were driving. Multi-use tools solve the problem of having to deal with many different tools.

Use by other animals


Tool use by animals is a phenomenon in which an animal uses any kind of tool in order to achieve a goal such as acquiring food and water, grooming, defense, communication, recreation or construction.[42] Originally thought to be a skill possessed only by humans, some tool use requires a sophisticated level of cognition.[43] There is considerable discussion about the definition of what constitutes a tool and therefore which behaviours can be considered true examples of tool use.[42][44] Observation has confirmed that a number of species can use tools including monkeys, apes, elephants, several birds, and sea otters. Now the unique relationship of humans with tools is considered to be that we are the only species that uses tools to make other tools.[42][45]

A Bonobo at the San Diego Zoo "fishing" for termites

Primates are well known for using tools for hunting or gathering food and water, cover for rain, and self-defense. Chimpanzees have often been the object of study in regard to their usage of tools, most famously by Jane Goodall; these animals are closely related to humans. Wild tool-use in other primates, especially among apes and monkeys, is considered relatively common, though its full extent remains poorly documented, as many primates in the wild are mainly only observed distantly or briefly when in their natural environments and living without human influence.[42][44] Some novel tool-use by primates may arise in a localized or isolated manner within certain unique primate cultures, being transmitted and practiced among socially connected primates through cultural learning.[43] Many famous researchers, such as Charles Darwin in his book The Descent of Man, mentioned tool-use in monkeys (such as baboons).[42][44][46]

Among other mammals, both wild and captive elephants are known to create tools using their trunks and feet, mainly for swatting flies, scratching, plugging up waterholes that they have dug (to close them up again so the water does not evaporate), and reaching food that is out of reach. Many other social mammals particularly have been observed engaging in tool-use. A group of dolphins in Shark Bay uses sea sponges to protect their beaks while foraging. Sea otters will use rocks or other hard objects to dislodge food (such as abalone) and break open shellfish. Many or most mammals of the order Carnivora have been observed using tools, often to trap or break open the shells of prey, as well as for scratching.[42][44][46]

Corvids (such as crows, ravens and rooks) are well known for their large brains (among birds) and tool use. New Caledonian crows are among the only animals that create their own tools. They mainly manufacture probes out of twigs and wood (and sometimes metal wire) to catch or impale larvae. Tool use in some birds may be best exemplified in nest intricacy. Tailorbirds manufacture 'pouches' to make their nests in. Some birds, such as weaver birds, build complex nests utilizing a diverse array of objects and materials, many of which are specifically chosen by certain birds for their unique qualities. Woodpecker finches insert twigs into trees in order to catch or impale larvae. Parrots may use tools to wedge nuts so that they can crack open the outer shell of nuts without launching away the inner contents. Some birds take advantage of human activity, such as carrion crows in Japan, which drop nuts in front of cars to crack them open.[42][44][46]

Several species of fish use tools to hunt and crack open shellfish, extract food that is out of reach, or clear an area for nesting. Among cephalopods (and perhaps uniquely or to an extent unobserved among invertebrates), octopuses are known to use tools relatively frequently, such as gathering coconut shells to create a shelter or using rocks to create barriers.[42][44][46]

Non-material usage


By extension, concepts which support systematic or investigative thought are often referred to as "tools", for example Vanessa Dye refers to "tools of reflection" and "tools to help sharpen your professional practice" for trainee teachers,[47] illustrating the connection between physical and conceptual tools by quoting the French scientist Claude Bernaud:

we must change [our ideas] when they have served their purpose, as we change a blunt lancet that we have used long enough.[47]

Similarly, a decision-making process "developed to help women and their partners make confident and informed decisions when planning where to give birth" is described as a "Birth Choice tool":

The tool encourages women to consider out-of-hospital settings where appropriate,[48]

and the idea of a "toolkit" is used by the International Labour Organization to describe a set of processes applicable to improving global labour relations.[49]

A telephone is a communication tool that interfaces between two people engaged in conversation at one level. It also interfaces between each user and the communication network at another level. It is in the domain of media and communications technology that a counter-intuitive aspect of our relationships with our tools first began to gain popular recognition. John M. Culkin famously said, "We shape our tools and thereafter our tools shape us".[50] One set of scholars expanded on this to say: "Humans create inspiring and empowering technologies but also are influenced, augmented, manipulated, and even imprisoned by technology".[51]

See also



  1. ^ Beck, Benjamin B. (1980). Animal tool behavior: the use and manufacture of tools by animals. New York: Garland STPM Pub. ISBN 0-8240-7168-9. OCLC 5607368. Archived from the original on 2022-08-29. Retrieved 2022-08-28.
  2. ^ Shumaker, Robert W.; Walkup, Kristina R.; Beck, Benjamin B. (2 May 2011). Animal Tool Behavior: The Use and Manufacture of Tools by Animals. JHU Press. ISBN 978-0801898532. Archived from the original on 29 August 2022. Retrieved 28 August 2022.
  3. ^ Finn, Julian K.; Tregenza, Tom; Norman, Mark D. (2009). "Defensive tool use in a coconut-carrying octopus". Curr. Biol. 19 (23): R1069–R1070. doi:10.1016/j.cub.2009.10.052. PMID 20064403. S2CID 26835945.
  4. ^ Jones, T. B.; Kamil, A. C. (1973). "Tool-making and tool-using in the northern blue jay". Science. 180 (4090): 1076–1078. Bibcode:1973Sci...180.1076J. doi:10.1126/science.180.4090.1076. PMID 17806587. S2CID 22011846. Archived from the original on 2022-05-10. Retrieved 2022-08-28.
  5. ^ Tom L. Beauchamp; R.G. Frey, eds. (2011). The Oxford Handbook of Animal Ethics. Oxford University Press. p. 232. ISBN 978-0195-3719-63.
  6. ^ Miller, Terry E. (2001). Sam, Sam-Ang. Oxford Music Online. Oxford University Press. doi:10.1093/gmo/9781561592630.article.49387. Archived from the original on 2022-07-30. Retrieved 2021-01-27.
  7. ^ Whiten, David J.; Whiten, Phyllis (April 2009). "Why Are Things Shaped the Way They Are?". Teaching Children Mathematics. 15 (8): 464–472. doi:10.5951/tcm.15.8.0464. ISSN 1073-5836. Archived from the original on 2022-07-30. Retrieved 2021-01-27.
  8. ^ Jones, S.; Martin, R.; Pilbeam, D., eds. (1994). The Cambridge Encyclopedia of Human Evolution. Cambridge: Cambridge University Press. ISBN 978-0-521-32370-3. Also ISBN 0-521-46786-1 (paperback)
  9. ^ McPherron, Shannon P.; Zeresenay Alemseged; Curtis W. Marean; Jonathan G. Wynn; Denne Reed; Denis Geraads; Rene Bobe; Hamdallah A. Bearat (2010). "Evidence for stone-tool-assisted consumption of animal tissues before 3.39 million years ago at Dikika, Ethiopia". Nature. 466 (7308): 857–60. Bibcode:2010Natur.466..857M. doi:10.1038/nature09248. PMID 20703305. S2CID 4356816.
  10. ^ Sahnouni, Mohamed; Semaw, Sileshi; Rogers, Michael (2013-07-04). "The African Acheulean". Oxford Handbooks Online. doi:10.1093/oxfordhb/9780199569885.013.0022. Archived from the original on 2022-07-30. Retrieved 2021-01-27.
  11. ^ "Rethinking Concepts and Theories". Gendered Innovations. Retrieved 19 January 2023.
  12. ^ Holmes, Bob. "Man's early hunting role in doubt". Newscientist.com. Archived from the original on 12 June 2015. Retrieved 12 November 2012.
  13. ^ Hollister-Short, Graham; James, Frank (2016). History of Technology Volume 12. London: Bloomsbury Publishing. ISBN 978-1-350-01858-7. OCLC 957126707. Archived from the original on 2022-08-29. Retrieved 2022-08-29.
  14. ^ Selin, Helaine, ed. (2008). Encyclopaedia of the history of science, technology, and medicine in non-western cultures (2nd ed.). Berlin: Springer. ISBN 978-1-4020-4425-0. OCLC 261324840. Archived from the original on 2022-08-29. Retrieved 2022-08-29.
  15. ^ Headrick, Daniel R. (2009). Technology: a world history. Oxford: Oxford University Press. ISBN 978-0-19-971366-0. OCLC 320625444. Archived from the original on 2022-08-29. Retrieved 2022-08-29.
  16. ^ Moorey, Peter Roger Stuart (1999). Ancient Mesopotamian Materials and Industries: The Archaeological Evidence. Eisenbrauns. ISBN 9781575060422.
  17. ^ D.T. Potts (2012). A Companion to the Archaeology of the Ancient Near East. p. 285.
  18. ^ Attema, P. A. J.; Los-Weijns, Ma; Pers, N. D. Maring-Van der (December 2006). "Bronocice, Flintbek, Uruk, JEbel Aruda and Arslantepe: The Earliest Evidence Of Wheeled Vehicles In Europe And The Near East". Palaeohistoria. 47/48. University of Groningen: 10–28 (11).
  19. ^ Paipetis, S. A.; Ceccarelli, Marco (2010). The Genius of Archimedes – 23 Centuries of Influence on Mathematics, Science and Engineering: Proceedings of an International Conference held at Syracuse, Italy, June 8–10, 2010. Springer Science & Business Media. p. 416. ISBN 9789048190911.
  20. ^ Faiella, Graham (2006). The Technology of Mesopotamia. The Rosen Publishing Group. p. 27. ISBN 9781404205604. Archived from the original on 2020-01-03. Retrieved 2022-08-29.
  21. ^ a b Moorey, Peter Roger Stuart (1999). Ancient Mesopotamian Materials and Industries: The Archaeological Evidence. Eisenbrauns. p. 4. ISBN 9781575060422.
  22. ^ Woods, Michael; Mary B. Woods (2000). Ancient Machines: From Wedges to Waterwheels. USA: Twenty-First Century Books. p. 58. ISBN 0-8225-2994-7. Archived from the original on 2020-01-04. Retrieved 2022-08-29.
  23. ^ S Dalley, The Mystery of the Hanging Gardens of Babylon, Oxford University Press(2013)
  24. ^ T Jacobsen and S Lloyd, Sennacherib's Aqueduct at Jerwan, Chicago University Press, (1935)
  25. ^ Terry S. Reynolds, Stronger than a Hundred Men: A History of the Vertical Water Wheel, JHU Press, 2002 ISBN 0-8018-7248-0, p. 14
  26. ^ Selin, Helaine (2013). Encyclopaedia of the History of Science, Technology, and Medicine in Non-Westen Cultures. Springer Science & Business Media. p. 282. ISBN 9789401714167. Archived from the original on 2022-04-09. Retrieved 2022-08-29.
  27. ^ "Waterwheel | History, Types & Uses". Britannica.
  28. ^ a b c Rolt, L.T.C. (1965). A Short History of Machine Tools. MIT Press. ISBN 9780262180139.
  29. ^ a b c Allen, Robert C. (2017). The Industrial Revolution: a very short introduction. [Oxford]. ISBN 978-0-19-178545-0. OCLC 981387269.{{cite book}}: CS1 maint: location missing publisher (link)
  30. ^ Hounshell, David A. (1984). From the American System to Mass Production, 1800–1932: The Development of Manufacturing Technology in the United States. Baltimore, Maryland: Johns Hopkins University Press. ISBN 978-0-8018-2975-8. LCCN 83016269. OCLC 1104810110.
  31. ^ Roe, Joseph Wickham (1916). English and American Tool Builders. New Haven, Connecticut: Yale University Press. LCCN 16011753. Reprinted by McGraw-Hill, New York and London, 1926 (LCCN 27-24075); and by Lindsay Publications, Inc., Bradley, Illinois, (ISBN 978-0-917914-73-7).
  32. ^ Kohlmaier, Georg; von Santory, Barna (1990). Houses of glass: a nineteenth-century building type (1st ed.). Cambridge, Mass.: MIT Press. ISBN 0-262-61070-1. OCLC 27334646.
  33. ^ Whelan, David (2012-10-25). "Nanotechnology: Big Potential In Tiny Particles - Forbes.com". Forbes. Archived from the original on 2012-10-25. Retrieved 2021-01-27.
  34. ^ Arabe, Katrina C. "Will this Tiny Science Usher in the Next Industrial Revolution?". www.thomasnet.com. Archived from the original on 2021-02-24. Retrieved 2021-01-27.
  35. ^ "Great Gouges: the Essential Tool Kit". September 4, 2017.
  36. ^ M, Saif (April 12, 2023). "Different Types of Cutting Tools & Their Uses [Names & PDF]". The Engineers Post.
  37. ^ "The Dos And Don'ts Of Using A Torque Wrench". My Auto Machine. April 27, 2023.
  38. ^ "Personal Protective Equipment (PPE) Safety". SafetyCulture. July 5, 2018.
  39. ^ a b "What to Use Instead of a Hammer: A Comprehensive Guide". toolstale.com. September 19, 2023.
  40. ^ "What are the best accessories and attachments to enhance the functionality of a power drill?". PowerTools.reviews. August 20, 2023.
  41. ^ "The History of Multi-Tools". Gallantry. 11 August 2016. Retrieved 31 August 2023.
  42. ^ a b c d e f g h Shumaker, Robert W.; Kristina R., Walkup; Beck, Benjamin; Burghardt, Gordon M. (2011). Animal tool behavior: the use and manufacture of tools by animals (2nd ed.). Baltimore: JHU Press. ISBN 978-1-4214-0128-7. OCLC 1269071005. Archived from the original on 2022-08-29. Retrieved 2022-08-28.
  43. ^ a b Waal, F. B. M. de (2016). Are we smart enough to know how smart animals are? (1st ed.). New York: Norton & Company. ISBN 978-0-393-24619-3. OCLC 947844682. Archived from the original on 2022-08-29. Retrieved 2022-08-28.
  44. ^ a b c d e f Sanz, Crickette Marie; Call, Josep; Boesch, Cristophe, eds. (2013). Tool use in animals: cognition and ecology. Cambridge: Cambridge University Press. ISBN 978-1-107-33647-6. OCLC 828424636. Archived from the original on 2022-08-29. Retrieved 2022-08-28.
  45. ^ Bjorklund, David F.; Bering, Jesse M. (5 June 1997). "Big brains, slow development and social complexity:The development and evolutionary origins of social cognition". In Cooper, Cary L. (ed.). International review of industrial and organizational psychology. Robertson, Ivan T. John Wiley and Sons. p. 113. ISBN 978-0-471-96111-6. Archived from the original on 6 January 2017. Retrieved 10 July 2011.
  46. ^ a b c d Choe, Jae C. (2019). Encyclopedia of animal behavior (2nd ed.). Amsterdam: Academic Press. ISBN 978-0-12-813252-4. OCLC 1088561040. Archived from the original on 2022-08-29. Retrieved 2022-08-28.
  47. ^ a b Dye, V. (2011) "Reflection, Reflection, Reflection. I’m thinking all the time, why do I need a theory or model of reflection?", in McGregor, D. and Cartwright, L. (eds.) Developing Reflective Practice: A guide for beginning teachers, Maidenhead: McGraw-Hill Education, p. 217
  48. ^ National Institute for Health and Clinical Excellence, The Birth Choice tool from Which?, published March 2016, accessed 11 February 2023
  49. ^ "The ILO Industrial Relations Global Toolkit". www.ilo.org. 2022-05-06. Retrieved 2023-03-11.
  50. ^ Culkin, John (March 18, 1967). "A Schoolman's Guide to Marshall McLuhan". The Saturday Review: 51–53.
  51. ^ Hurme, Pertti; Jouhki, Jukka (2017). "We Shape Our Tools, and Thereafter Our Tools Shape Us". Human Technology. 13 (2): 145. doi:10.17011/ht/urn.201711104209. Retrieved 20 January 2023.
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