1. von Neumann J.,Mathematische Grundlagen der quantenmechanik (Julius Springer, Berlin) 1932;Mathematical Foundations of Quantum Mechanics, translated byR. T. Beyer (Princeton University Press, Princeton, N.J.) 1955, especially p. 167 of the original. I have translated «... es ist zweckmÄssig anzunehmen,...» as «... it is appropriate to assume,...» instead of Beyer’s «... it is convenient to assume, ...». My dictionary prefers «suitable for the object in view».
2. Yang C. N. andTiomno J.,Phys. Rev.,79 (1950) 495.
3. Zharkov G. F.,Sov. Phys. JETP,20 (1950) 492.
4. Orear J., Rosenfeld A. H. andSchluter R. A. (Editors),Proceedings of the International Conference, Nuclear Physics and the Physics of Fundamental Particles,September 17–22, 1951, sect. IIC. On the inversion properties of spin-(l/2) fields, see pp. 109–110, reported by Morris Scharff.
5. Wick G. C., Wightman A. S. andWigner E. P.,Phys. Rev.,88 (1952) 101.