https://doi.org/10.26485/0459-6854/2018/68.2/3 The paper deals with the following problem stated by V.N. Dubinin and earlier in different form by G.P. Bakhtina.
https://doi.org/10.26485/0459-6854/2018/68.2/3 Praca dotyczy zagadnienia postawionego przez V. N. Dubinina, a przedtem w innej postaci przez G. P. Bakhtina.