Hembars’ka, S. B., & Zaderei, P. V. (2016). Estimations of the integral of modulus for mixed derivatives of the sum of double trigonometric series. Ukrains’kyi Matematychnyi Zhurnal, 68(7), 908-921. Retrieved from https://umj.imath.kiev.ua/index.php/umj/article/view/1890