Volume 17, No 6, 2010, P.
UDC K
Abstract: We
Keywords:
Yu 1,2 Al 2 1. S. L. Sobolev Institute of Mathematics, SB RAS, 4 Acad. Koptyug Ave., 630090 Novosibirsk, Russia 2. Novosibirsk State University, 2 Pirogov St., 630090 Novosibirsk, Russia e-mail: