H. MAHMOOD, AKRAM, RAID S. KARYAKOS, and LAMYAA H. SAADOON. “Solvability Conditions For A System Of Nonhomogenous Differntial Equations Of The First Order”. Journal of Education and Science (JES) 21, no. 2 (June 1, 2008): 150–154. Accessed August 7, 2025. https://ojs.uomosul.edu.iq/index.php/edusj/article/view/24426.