1. J. D. Anderson, C. Wong and J. W. McClure, Phys. Rev. 126 2170 (1962);
2. A. K Kerman, in “Nuclear Isospin’ (J. D. Anderson, S. D. Bloom, J. Cerny and W. W. True, Eds.), p. 315, Academic Press, New York (1969).
3. For a review of charm, see M. K. Gaillard, B. W. Lee and J. Rosner, Rev. Mod. Phys. 47 277(1975)
4. S. Okubo, Phys. Letters 5 165(1963)
5. G. Zweig, unpublished, 1964; and in Symmetries in Elementary Particle Physics ( Academic Press, New York, 1965 ) p. 192.