For citations:
Ivankov P.L. . Chebyshevskii Sbornik. 2020;21(2):159-168. (In Russ.) https://doi.org/10.22405/2226-8383-2020-21-2-159-168
Ivankov P.L. . Chebyshevskii Sbornik. 2020;21(2):159-168. (In Russ.) https://doi.org/10.22405/2226-8383-2020-21-2-159-168