1. M. Gell-Mann, Phys. Lett. 8, 214 (1964)
2. G. Zweig, An $${\mathsf{SU(3)}}$$ model for the strong interaction symmetry and its breaking, CERN-TH-401, 412 (1964)
3. M. Gell-Mann, Y. Neemam, The Eightfold Way: A Review With a Collection of Reprints, (Benjamin Press, New York , 1964), pp. 317.
4. J.J.J. Kokkedee, The Quark Model (Benjamin Press, New York, 1969), p. 239
5. F.E. Close, An Introduction to Quarks and Partons (Academic Press, London, 1979), p. 481