1. P. A. M. Dirac, Proc. Roy. Soc. A 109 (1925), 642–653.
2. B. L. van der Waerden, Sources of Quantum Mechanics, Dover, 1967, 307–320; this source book will be referred to as SQM.
3. W. Heisenberg, Zeit. Phys. 33 (1925), 879–893; see also SQM, 261–276.
4. M. Born and P. Jordan, Zeit. Phys. 34 (1925), 858–888; SQM, 277–306.
5. M. Born, W. Heisenberg, and P. Jordan, Zeit. Phys. 35 (1926), 557–615.