1. F. P. Vasil’ev, Methods for Solving Extremal Problems (Nauka, Moscow, 1981) [in Russian].
2. A. N. Tikhonov, A. S. Leonov, and A. G. Yagola, Nonlinear Ill-Posed Problems (Fizmatlit, Moscow, 1995; CRC, London, 1997).
3. A. B. Bakushinskii and M. Yu. Kokurin, Iterative Methods for Solving Ill-Posed Operator Equations with Smooth Operators (Editorial URSS, Moscow, 2002) [in Russian].
4. A. B. Bakushinskii and M. Yu. Kokurin, Algorithmic Analysis of Irregular Operator Equations (URSS, Moscow, 2012) [in Russian].
5. B. Kaltenbacher, A. Neubauer, and O. Scherzer, Iterative Regularization Methods for Nonlinear Ill-Posed Problems (Walter de Gruyter, Berlin, 2008).