Tepnadze T. On the approximation properties of Cesàro means of negative order of double Vilenkin – Fourier series. Ukr. Mat. Zhurn. [Internet]. 2020 Mar. 28 [cited 2025 Dec. 5];72(3):391-406. Available from: https://umj.imath.kiev.ua/index.php/umj/article/view/6045