root, root. “Comparison of Two Methods Maximum Likelihood and Weighted Least Square Method to Estimate of Survival Function (exponential - Second Order Gamma) Mixed Distribution”. Warith Scientific Journal 3, no. 6 (June 30, 2021): 161-185. Accessed January 11, 2026. https://wsj.uowa.edu.iq/index.php/warith/article/view/559.