A. Sommerfeld and N. H. Frank
Rev. Mod. Phys. 3, 1 (1931) - Published 1 January, 1931
E. U. Condon and P. M. Morse
Rev. Mod. Phys. 3, 43 (1931) - Published 1 January, 1931
Robert S. Mulliken
Rev. Mod. Phys. 3, 89 (1931) - Published 1 January, 1931
H. A. Wilson
Rev. Mod. Phys. 3, 156 (1931) - Published 1 January, 1931
L. W. McKeehan
Rev. Mod. Phys. 3, 190 (1931) - Published 1 January, 1931
