1. B.D. ANNIN, Existence and uniqueness of the solution of the elastic-plastic torsion problem, for a cylindrical bar of oval cross-section, Prikl. Mat. Meh. 29 (1965).
2. A.M.ARTHURS, Complementary variational principles, Clarendon Press Oxford, 1970.
3. E.ASPLUND, Positivity of duality mappings, Bull. Amer. Math. Soc. 73 (1967), 200–203.
4. J.P.AUBIN, Approximation of variational inequalities, in “Functional Analysis and Optimization” (E. R. Caianiello Ed.), Acad. Press 1966, 7–14.
5. Approximation des espaces de distributions et des opeéra-teurs différentiels, Bull. Soc. Math. France, Mémoire 12 (1967),1–139.