1. R.F. Alvarez-Estrada, F. Fernandez, J.L. Sanchez-Gomez, V. Vento: Models of Hadron Structure Based on Quantum Chromodynamics, Lect. Notes Phys., Vol. 259 (Springer, Berlin, Heidelberg, New York 1986).
2. A. Chodos, R.C. Jaffe, K. Johnson, C.B. Thorn, V.F. Weisskopf: Phys. Rev. D9, 3471 (1974).
3. A. Chodos, C.B. Thome, V.F. Weisskopf: Phys. Rev. D12, 2733 (1975).
4. See W. Greiner and B. Müller: Quantum Mechanics — Symmetries (Springer, Berlin, Heidelberg, New York 1992).
5. See also F.E. Close: Introduction to Quarks and Partons (Academic Press, London 1979).