1. Variational Methods for the Study of Nonlinear Operators;Vainberg,1964
2. Variational Methods in Theoretical Mechanics;Oden,1981
3. Complementary minimum principles for an elastic–plastic material;Greenberg;Quart. Appl. Math.,1949
4. Theory of Perfect Plastic Solids;Prager,1951
5. Variational principles in the mathematical theory of plasticity;Drucker,1958