1. M. Gell-Mann, Phys. Lett. 8, 214 (1964)
2. G. Zweig, CERN Rept. 8182/Th401 (1964)
3. M. Gell-Mann, Y. Ne'eman, The eightfold way (W.A. Benjamin, Inc., 1964)
4. R.H. Dalitz (1967), reprinted in Selected Lectures of Hawaii Topical Conference, Vol. 1, edited by S. Pakvasa, S.F. Tuan (World Scientific, Singapore 1982)
5. D. Faiman, A.W. Hendry, Phys. Rev. 173, 1720 (1968)