1. Yu. G. Reshetnyak, Space Mappings with a Bounded Distortion [in Russian], Nauka, Novosibirsk (1982).
2. Yu. G. Reshetnyak, Lectures on Mathematical Analysis [in Russian], Novosibirsk University Press, Novosibirsk (1972).
3. V. G. Maz'ya, ?On the behavior in the vicinity of the boundary of a solution of the Dirichlét problem for an elliptic equation of the second order in the divergent form,? Mat. Zametki,2, No. 2, 209?220 (1967).
4. O. A. Oleinik and G. A. Iosif'yan, ?An analog of de Saint-Venant's principle and the uniqueness of solutions of the boundary problem in unbounded domains for parabolic equations of the second order,? Usp. Mat. Nauk,41, No. 6, 142?166 (1976).
5. O. A. Oleinik, Lectures on Partial Differential Equations [in Russian], Moscow University Press, Moscow (1976).