Younis, M. T., and W. Al-Hayani. “Solving Fuzzy System for Volterra-Fredholm Integral Equations of the Second Kind Using Homotopy Perturbation Method”. Results in Nonlinear Analysis, vol. 8, no. 2, July 2025, pp. 207–221, https://www.nonlinear-analysis.com/index.php/pub/article/view/625.