Lal, Shyam, and Hare Krishna Nigam. “Degree of Approximation by $ (N, P, Q) $ Summability Means of the Fourier-Laguerre Expansion”. Tamkang Journal of Mathematics 32, no. 2 (June 30, 2001): 143–150. Accessed July 22, 2024. https://journals.math.tku.edu.tw/index.php/TKJM/article/view/357.