1. Gilbarg, D., and Trudinger, N.S. (1983). Elliptic Partial Differential Equations of Second Order, Springer. [2nd ed.].
2. Primal-dual weak Galerking finite element methods for elliptic Cauchy problems;Comput. Math. Appl.,2020
3. Bifurcatioin perturbation of simple eigenvalues, and linearized stability;Arch. Ration. Mech. Anal.,1973
4. Lions, J.L. (1983). Gauthier-Villars.
5. Sur les problèmes aux deriveés partielles et leur signification physique;Bull. Univ. Princeton.,1902