1. M. A. Grinfel'd, Methods of Continuum Mechanics in the Theory of Phase Transitions [in Russian], Nauka, Moscow (1990).
2. E. Giusti, Minimal Surfaces and Functions of Bounded Variation [Russian translation], Mir, Moscow (1989).
3. A. Kufner and S. Fučik, Nonlinear Differential Equations [Russian translation], Nauka, Moscow (1988).