Pontryagin maximum principle for semilinear second order elliptic partial differential equations and variational inequalities with state constraints
In this remarkable paper a general optimal control problem is considered with various kinds of state constraints and differential inclusions as side conditions. The author uses successfully Ekeland's variational principle and Green's functions (for the linear elliptic part of the variational inequality) together with the spike variation technique for elliptic equations and gives full proofs and a lot of limits concerning other papers of this topic.
scientific article; zbMATH DE number 94955