1. P. A. M. Dirac, Lectures on Quantum Field Theory (Academic, New York, 1966).
2. L. D. Landau, Collected Works, Ed. by E. M. Lifshitz and I. M. Khalatnikov (Nauka, Moscow, 1969), pp. 421–424.
3. I. E. Tamm, Collected Works (Nauka, Moscow, 1976), Vol. 2.
4. Physics Encyclopedia, Ed. by Yu. V. Prokhorov (Bol’shaya Ross. Entsiklopediya, Moscow, 2003).
5. R. Feynman, QED: The Strange Theory of Light and Matter (Princeton Univ. Press, Princeton, NJ, 1985).