Solution of an inverse problem for estimation of ionospheric parameters

G. V. Grudinskaya, Propagation of Radio Waves [in Russian], Nauka, Moscow (1977). F. P. Vasil'ev, Numerical Methods of Solution of Extremal Problems [in Russian], Nauka, Moscow (1988). Ph. Gill, W. Murray, and M. Wright, Practical Optimization, Academic Press, New York (1981). A. N. Tikhonov and V. Ya. Arsenin, Methods of Solution of Some Ill-Posed Problems [in Russian], Nauka, Moscow (1974). F. P. Vasil'ev, Methods of Solution of Extremal Problems [in Russian], Nauka, Moscow (1984).