“…In (L. Arkeryd, 1969), L p − estimates for solutions were studied, under the condition that the coefficients of leading derivatives are infinitely differentiable, and in (L. A. Bagirov, 1979;S. V. Uspenskii, G. V. Demidenko and V. G. Perepelkin, 1984) some other problems of the theory of quasielliptic equations were considered.…”