L. Rempulska and Z. Walczak, “On modified Picard and Gauss—Weierstrass singular integrals”, Ukr. Mat. Zhurn., vol. 57, no. 11, pp. 1577–1584, Nov. 2005, Accessed: Dec. 05, 2025. [Online]. Available: https://umj.imath.kiev.ua/index.php/umj/article/view/3710