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2. Survey lectures on the mathematical foundations of the finite element method;Babuška,1972
3. Finite-dimensional approximation of nonlinear problems. Part I: Branches of nonsingular solutions;Brezzi;Numer. Math.,1980
4. The Finite Element Method for Elliptic Problems;Ciarlet,1978
5. M. Crouzeix, Approximation des probléms faiblement non linèaires, (to appear).