Abd-Elhameed, Waleed M. M. “An Elegant Operational Matrix Based on Harmonic Numbers: Effective Solutions for Linear and Nonlinear Fourth-Order Two Point Boundary Value Problems”. Nonlinear Analysis: Modelling and Control 21, no. 4 (July 21, 2016): 448–464. Accessed July 18, 2024. https://www.journals.vu.lt/nonlinear-analysis/article/view/13454.