1. O. Stem, Z Phys., 7 (1921) 249;
2. W. Gerlach, O. Stem, ibidem, 8 (1922) 110;
3. W. Gerlach, O. Stem, ibidem, 9 (1922) 353.
4. G. Goudsmit, S. Uhlenbeck, Naturwissenschaften, 13 (1925) 953.
5. H. Corben, Classical and Quantum Theories of Spinning Particles (Holden-Day, San-Fransisco) 1968;