Aslam Noor , MuhammadNoor , Khalida InayatWaheed , Asif and Al-Said , Eisa. (2012). Variation of Parameters Method for Solving System of Nonlinear Volterra Integro-Differential Equation.
Advances in Applied Mathematics and Mechanics. 4 (2).
190-204.
doi:10.4208/aamm.10-m1118