1. O. A. Ladyzhenskaya (Ladyzenskaja), V. A. Solonnikov, and N. N. Ural'tseva (Ural'ceva), Linear and Quasilinear Equations of Parabolic Type, Am. Math. Soc., Providence (1968).
2. O. A. Ladyzhenskaya and N. N. Ural'tseva, Linear and Quasilinear Elliptic Equations, Academic Press, New York (1968).
3. J. Serrin, ?The problem of Dirichlet for quasilinear elliptic differential equations with many independent variables,? Philos. Trans. Roy. Soc. London, Ser. A, Math. Phys. Sci.,264, 1153, 413?496 (1969).
4. A. V. Ivanov, ?The Dirichlet problem for quasilinear nonuniform elliptic equations of the second order,? Zap. Nauchn. Sem. LOMI,19, 79?94 (1970); Tr, MIAN SSSR,116, 34?54 (1971).
5. A. V. Ivanov, ?On the structure of quasilinear elliptic equations of the second order,? Zap. Nauchn. Sem. LOMI,21, 5?33 (1971).