1. Bjorken, J. D. and Drell, S. D. (1965).Relativistic Quantum Fields. McGraw-Hill, New York.
2. Heisenberg, W. (1938).Annalen der Physik,32, 20.
3. Jaffe, J. and Shapiro, I. I. (1972).Physical Review,6D, 405.
4. K�lnay, A. J. (1971).Studies in the Foundations, Methodology and Philosophy of Science, Vol. 4, p. 104. Springer-Verlag, Berlin.
5. K�lnay, A. J. and Toledo, B. P. (1967).Nuovo Cimento,48, 997.