The Historical Development of Quantum Theory, Vol. 3: The Formulation of Matrix Mechanics and Its Modifications, 1925-1926 by Jagdish Mehra and Helmut Rechenberg, Springer-Verlag, New York, 1982, p. 129, footnote 146. In Mehra and Rechenberg's system of reference to transcriptions of taped conversations, this quote is cited as: Born, Conversations, p. 48.
This quote is used as an epigraph on p. 330 in Operator Commutation Relations by Palle E. T. Jorgensen and Robert T. Moore, D. Reidel, Dordrecht / Boston / Lancaster, 1984.
Some interesting links for Max Born:
Born [in the MacTutor History of Mathematics archive at the University of St Andrews]
Max Born Winner of the 1954 Nobel Prize in Physics
Surprises in Writing a Biography of Max Born by Nancy Greenspan
I guess the pioneers in quantum theory have more representation on the web than most pure mathematicians.
to Quotes selected by Palle Jorgensen