1. Case, K. M. (1957).Physical Review 107, 307.
2. Frampton, P., Glashow, S. L., and Yildiz, A. (eds.) (1980).First Workshop on grandunification (Math Sci. Press., Brookline, Massachusetts).
3. Gursey, F. (1958).Nuovo Cimento 7, 411.
4. Kabir, P. K. (ed.) (1963).The Development of Weak Interaction Theory (Gordon and Breach, New York).
5. Majorana, E. (1932).Nuovo Cimento 9, 335.