Dissertation title: Diffraction from a Plane Screen. P. S. Epstein Beugung an einem ebenen Schirm Dissertation, Munich, 1914. As cited in: Eckart Paper – Carl Eckart The Solution of the Problem of the Simple Oscillator by a Combination of the Schrödinger and the Lanczos Theories, Proceedings of the National Academy of Sciences of the United States of America12 473-476 (1926). California Institute of Technology. Communicated May 31, 1926.