Danilin, A. R. Approximation of a singularly perturbed elliptic problem of optimal control. (English. Russian original) Zbl 0983.49018 Sb. Math. 191, No. 10, 1421—1431 (2000); translation from Mat. Sb. 191, No. 10, 3-12 (2000). Reviewer: Uldis Raitums (Riga) MSC: 49K20 35B25 35B37 93C20 49K40