1. V. Barbu and Th. Precupanu, “Convexity and Optimization in Banach Spaces”, Sijthoff & Noordhoff, International Publishers, 1978.
2. J. Berkovits and V. Mustonen, Topological degree for perturbations of linear maximal monotone mappings and applications to a class of parabolic problems, Rend. Mat. Appl. (7) 12 (1992), 597–621.
3. S. Carl, A combined variational-monotone iterative method for elliptic boundary value problems with discontinuous nonlinearity, Appl. Anal. 43 (1992), 21–45.
4. S. Carl and S. Heikkilä, On extremai solutions of an elliptic boundary value problem involving discontinuous nonlinearities, Differential and Integral Equations 5 (1992), 581–589.
5. S. Carl, S. Heikkilä and V. Lakshmikantham, Nonlinear elliptic differential inclusions governed by state-dependent subdifferentials, Nonlinear Anal. 25 (1995), 729–745.