1. M. W. Evans, J.-P. Vigier, S. Roy, and S. Jeffers, The Enigmatic Photon, Volume Three: Theory and Practice of the Field, Chaps. 1 and 2., (Kluwer Academic, Dordrecht, 1996).
2. P. A. M. Dirac, Quantum Mechanics, 4th edn. revised, (Oxford University Press, Oxford, 1974).
3. L. H. Ryder, Quantum Field Theory, 2nd edn., (Cambridge University Press, Cambridge, 1987).
4. J. D. Bjorken and S. D. Drell, Relativistic Quantum Mechanics (McGraw Hill, New York, 1964).
5. C. Itzykson and J. B. Zuber, Quantum Field Theory (McGraw Hill, New York, 1980).