1. G. V. Efimov, Nonlocal Interactions of Quantitized Fields [in Russian], Nauka, Moscow (1977).
2. D. I. Blokhintsev, Preprint No. R2-12462, Joint Inst. for Nuclear Research, Dubna (1979), p. 7.
3. I. A. Khokhlov, Izv. Vyssh. Uchebn. Zaved., Fizika, No. 6, 109 (1996).
4. H. Yukawq, Phys. Rev.,80, 1047 (1950).
5. Z. Koba, Prog. Theor. Phys.,5, 696 (1950).