Hong Danh, Pham, and Huynh Hoang Dung. “LINEAR APPROXIMATION ASSOCIATED WITH THE SYSTEM OF NONLINEAR FUNCTIONAL- INTEGRAL”. Science and Technology Development Journal 6, no. 12 (December 31, 2003): 15-25. Accessed July 22, 2024. https://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/3390.