1. Compendium of Quantum Physics: Concepts, Experiments, History and Philosophy, edited by D. Greenberger, K. Hentschel, F. Weinert (Springer, Heidelberg, 2009)
2. I. Newton, Philosophiae Naturalis Principia Mathematica (Streator, London, 1687)
3. J.C. Maxwell, A Treatise on Electricity and Magnetism (Clarendon Press, Oxford, 1873)
4. M. Born, Z. Phys. 37, 863 (1926)
5. W. Gerlach, O. Stern, Z. Phys. 9, 353 (1922)