Гаврилків, В. М. (2019) “SEMIGROUPS OF LINKED UPFAMILIES”, PRECARPATHIAN BULLETIN OF THE SHEVCHENKO SCIENTIFIC SOCIETY. Number, (1(29), pp. 104–112. Available at: https://pvntsh.nung.edu.ua/index.php/number/article/view/145 (Accessed: 6 December 2025).