Citation:
N. N. Yanenko, “On non-linear equations of a variable type”, Boundary-value problems of mathematical physics and related problems of function theory. Part 12, Zap. Nauchn. Sem. LOMI, 96, "Nauka", Leningrad. Otdel., Leningrad, 1980, 294–301; J. Soviet Math., 21:5 (1983), 868–875