M. Alkawaz, Saad. “Estimate The Effect Of International Trade For Invironmental Services Sample From WTO Countries”. TANMIYAT AL-RAFIDAIN 37, no. 120 (December 1, 2018): 9–28. Accessed September 8, 2025. https://tanmiyat.uomosul.edu.iq/index.php/tanmiyat/article/view/29868.