Mahmoud, Abdelmotalab Osman, and Asim Ibrahim Mohamed. “The Effect of Operating Costs on Environmental Degradation under International Environmental Standards: Case Study - Khartoum State”. Journal of Economic, Administrative and Legal Sciences, vol. 4, no. 9, Aug. 2020, pp. 159-43, https://doi.org/10.26389/AJSRP.O080320.