1. R. W. Hamming, Numerical Methods for Scientists and Engineers (McGraw-Hill, New York, 1962; Nauka, Moscow, 1968).
2. D. Hilbert, Gessamelte Abhandlungen (Springer, Berlin, 1935), Vol. 3, pp 3–9.
3. A. I. Markushevich, Theory of Functions of a Complex Variable (Nauka, Moscow, 1968; Chelsea, New York, 1977).
4. T. A. Rakcheeva, “Approximation of Curves by Multifocus Lemniscates,” in Man-Machine Systems and Data Analysis (Nauka, Moscow, 1992), pp. 93–110 [in Russian].
5. T. A. Rakcheeva, “Approximation of Curves in the Complex Plane by Multifocus Lemniscates,” in Mathematics, Computer, and Education (Research Center Regular and Chaotic Dynamics, Moscow, 2008), Vol. 2, No. 15, pp. 68–75 [in Russian].