1. J. Kokkedee, The Quark Model in Particle Physics, Benjamin, New York (1969).
2. N. N. Bogolyubov, V. A. Matveev, Nguyen Van Hieu, D. Stoyanov, B. V. Struminskii, A. N. Tavkhelidze, and V. P. Shelest, Preprint JINR R-2141 [in Russian], Dubna (1965).
3. D. I. Blokhintsev, Nucl. Phys.,31, 628 (1962).
4. R. Feynman, Phys. Rev. Lett.,23, 1415 (1969).
5. P. N. Bogolyubov, Fiz. Elem. Chastits. At. Yadra,3, 144 (1972).