CONSTRUCTION OF FUNCTION-SPACES BY MEANS OF THE LAPLACIAN AND THE AVERAGING METHOD СтатьяZHIDKOV G.V.Differential Equations. Том 20. 1984. С. 477-485
VARIATIONAL METHOD FOR SOLVING BOUNDARY-VALUE-PROBLEMS FOR THE WAVE-EQUATION СтатьяFILIPPOV V.M.Differential Equations. Том 20. 1984. С. 1401-1407