1. 1. M. D. Kruskal, private communication, circa 1985.
2. 2. The Painlevé Property: One Century Later, edited by R. Conte, CRM Series in Mathematical Physics, Springer-Verlag, New-York (1999).
3. 3. B. Grammaticos and A. Ramani, Integrability – and How to Detect It, Lect. Notes Phys. 638, 31 (2004).
4. 4. R. Mills, Space, Time and Quanta: an introduction to contemporary physics W H Freeman & Co, (1994).
5. 5. A. Einstein, Physics and Reality in Essay in Physics, Philosophical Library, New York, 1950. R. P. Feynman, Intl. J. Theor. Phys. 21 (1982) 467. E. Witten, Reflections on the fate of spacetime, Physics Today, April 1996, p 24.