1. Y. Shibata, and H. Tezuka; Z. Phys. C 62 (1994) 533
2. L. Tomio, and P.L. Ferreira: Nuovo Cimento 107B (1992) 785
3. R.K. Bhaduri: Models of the nucleons, Reading Mass.: Addison-Wesley 1988; B Thaller: The Dirac equation, Berlin, Heidelber, New York: Springer 1992
4. J.D. Biorken, S.D. Drell; Relativistic quantum mechanics, New York: McGraw-Hill 1964, C. Itzykson, J.-B. Zuber; Quantum field theory, New York: McGraw0Hill 1985