1. P. Ehrenfest, Zur Krise der Lichtaether-Hypothese, in: 1959, P. Ehrenfest, Collected Scientific Papers, ed. M.J. Klein (North-Holland, Amsterdam) p. 306.
2. Between Man and Man;Buber,1948
3. Paul Ehrenfest in Memoriam;Einstein,1950
4. Reminiscences of Professor Paul Ehrenfest;Uhlenbeck;American Journal of Physics,1956