Petryshyn RI, Pokhyla OM. Estimate of an error of the averaging method on a semiaxis for a multifrequency resonance system. Ukr. Mat. Zhurn. [Internet]. 1997May25 [cited 2024Nov.24];49(5):685–690. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/5049