YANG, GOU-SHENG, and JYH-WEN LEU. “EFFECTIVE ESTIMATES FOR BOUNDARY VALUE PROBLEMS”. Tamkang Journal of Mathematics 25, no. 2 (June 1, 1994): 167–177. Accessed July 22, 2024. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/4440.