León, Víctor, and Bruno Scárdua. “Regularity, Synthesis, Rigidity and Analytic Classification for Linear Ordinary Differential Equations of Second Order”. Journal of AppliedMath 2, no. 4 (August 18, 2024): 1698. Accessed April 8, 2025. https://ojs.acad-pub.com/index.php/JAM/article/view/1698.