Neagu, N., D. Cozma, і M. Popa. 2017. INVARIANT METHODS FOR STUDYING STABILITY OF UNPERTURBED MOTION IN TERNARY DIFFERENTIAL SYSTEMS WITH POLYNOMIAL NONLINEARITIES. Буковинський математичний журнал 4 (3-4). https://bmj.fmi.org.ua/index.php/adm/article/view/219.