Hung, Tran Loc. “On Chi-Square Type Distributions With Geometric Degrees of Freedom in Relation to Geometric Sums”. VNUHCM Journal of Science and Technology Development 22, no. 1 (March 31, 2019): 180-184. Accessed September 1, 2025. https://stdj.scienceandtechnology.com.vn/index.php/stdj/article/view/1053.