Краснодембський, Адам Михайлович. “PERIODICITY OF DECISIONS OF SYSTEM OF TWO NONLINEAR DIFFERENTIAL EQUALIZATIONS OF THE THIRD ORDER”. PRECARPATHIAN BULLETIN OF THE SHEVCHENKO SCIENTIFIC SOCIETY. Number, no. 1(13), Mar. 2019, pp. 39-42, https://pvntsh.nung.edu.ua/index.php/number/article/view/260.