1. See, for example, the very interesting monograph byR. Weitzenböck:Der Vierdimensionale Raum (Braunschweig, 1929).
2. A slightly different statement of this proposition is customarily attributed toJ. Überweg:System der Logik (various editions, Bonn, 1857–1882), although it was probably known toG. Green and other mathematicians who studied problem inn dimensions somewhat earlier
3. P. Ehrenfest:Proc. Amsterdam Acad.,20, 200 (1917);Ann. Physik,61, 440 (1920).
4. For example, no reference is made to Ehrenfest’s work in the recent historical treatment ofK. Jammer:Concepts of Space (Cambridge, 1954); nor in the discussion ofH. Weyl:Philosophy of Mathematics and Natural Science (Princeton, 1949), p. 136.
5. G. J. Whitrow:The Structure and Evolution of the Universe (New York, 1959) Appendix.