Hashem, H.H.G., and A.M.A. El-Sayed. “SOLVABILITY OF COUPLED SYSTEMS OF FRACTIONAL ORDER INTEGRO-DIFFERENTIAL EQUATIONS”. Journal of the Indonesian Mathematical Society 19, no. 2 (March 4, 2014): 111–121. Accessed October 5, 2024. http://jims-a.org./index.php/jimsa/article/view/167.