- The paper shows that Conway's maximal surreal field is isomorphic as an ordered field to a maximal hyperreal field (in NBG) (see p. 35).
- Reviewer for MathSciNet wrote: "This ... comprehensive study on the early history of non-Archimedean mathematics ... provides an excellent survey of highest scholarly standards" here
- Ehrlich, Philip: Number systems with simplicity hierarchies: a generalization of Conway's theory of surreal numbers. Journal of Symbolic Logic 66 (2001), no. 3, 1231–1258.
- Real numbers, generalizations of the reals, and theories of continua. Edited by Philip Ehrlich. Synthese Library, 242. Kluwer Academic Publishers Group, Dordrecht, 1994.
- R. Gregory Taylor wrote: "Ehrlich has brought together some valuable work on issues of great interest to logicians and philosophers of mathematics" here.