Nobel prize to P. A. M. Dirac awarded in 1933. Co-winner E. Schrödinger "for the discovery of new productive forms of atomic theory''
Dirac, P.A.M.; The Quantum Theory of the Electron. Pt II
Proc. Roy. Soc. A118 (1928) 351;
The theory enunciated in Part I is further developed, commencing with a proof of the conservation theorem, which states that the change in probability of the electron being in a given volume during a given time is equal to the probability of its having crossed the boundary. The selection rule for j, the quantum number determining the magnitude of the resultant angular momentum for an electron in a central field of force, is worked out and found to be exactly equivalent to the two selection rules
for j and k, of the usual theory, which agree with experiment. The relative intensities of the Zeeman components of the lines in a combination doublet and the alteration of the energy levels by a magnetic field are investigated and the results shown to be in agreement with those of previous theories based on the spinning electron model. (Science Abstracts. 1928. 1507. W. S. S.).
Related references More (earlier) information appears in P. A. M. Dirac, Proc. Roy. Soc. A117 (1928) 610;
Relativistic wave equation for the electron and theory of the Zeeman effect.