“Weighted Least Squares Estimation of the Effect of Wastewater Pollution of Tigris River Wasit Governorate”. Journal of Economics and Administrative Sciences 24, no. 109 (December 1, 2018): 486. Accessed May 7, 2024. https://jeasiq.uobaghdad.edu.iq/index.php/JEASIQ/article/view/1573.