1. P. Zeeman, Doublets and triplets in the spectrum produced by external magnetic forces, The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, 44:266, 55, 1897.
2. F. Paschen and E. Back, Liniengruppen magnetisch vervollständigt [Line groups magnetically resolved], Physica (in German), 1, 261, 1921.
3. G. E. Uhlenbeck and S. Goudsmit, Spinning electrons and the structure of spectra, Naturwissenschaften, 47, 53, 1925
4. G. E. Uhlenbeck and S. Goudsmit, Spinning electrons and the structure of spectra, Nature, 117, 264, 1926.
5. P. A. M. Dirac, The quantum theory of the electron, Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences, 117, No.778, 610, 1928.