1. E. P. Wigner, Ann. Math. (2), 40, 149–204 (1939).
2. N. N. Bogolubov, A. A. Logunov, A. I. Oksak, and I. T. Todorov, General Principles of Quantum Field Theory [in Russian], Nauka, Moscow (1987); English transl., Kluwer, Dordrecht (1990).
3. I. M. Gel’fand and A. M. Yaglom, ZhETF, 18, No. 8, 703–733 (1948).
4. A. O. Barut and R. Raczka, Theory of Group Representations and Applications, World Scientific, Singapore (1986).
5. L. D. Landau and R. Peierls, Z. Phys., 69, 56–69 (1931).