A functional equation from theoretical physics
A. V. Yagzhev

References
1.	Bokov O.G., “Model polei Li i mnogovremennye zapazdyvayuschie funktsii Grina elektromagnitnogo polya v dielektricheskikh sredakh”, Nauchn. tr. Novosib. gosud. ped. in-ta, 86, 1973, 3–9
2.	Greenberg O.W., “Generalized free fields and models of local fields theory”, Ann. Phys., 16:2 (1961), 158–176