Danilin, A. R. On estimates optimal with respect to the order of finite-dimensional approximations of solutions of ill-posed problems. (Russian) Zbl 0585.47053 Zh. Vychisl. Mat. Mat. Fiz. 25, No. 8, 1123—1130 (1985). Reviewer: J.Kalinowski MSC: 47J25 65J15