H. MAHMOOD, AKRAM, اکرم, RAID S. KARYAKOS, رائد, LAMYAA H. SAADOON, and لمیاء. “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 4, 2025. https://rjps.uomosul.edu.iq/index.php/edusj/article/view/18404.