This publication is cited in the following articles:
G. M. Vodinchar, O. K. Zhdanova, A. S. Perezhogin, O. V. Sheremetyeva, T. P. Yakovleva, “Solutions of mathematical olympiad «Vitus Bering - 2016»”, Bulletin KRASEC. Phys. & Math. Sci., 13:2 (2016), 67–71