Team, Support. “Hyers-Ulam Stability of Linear Differential Equations y′′ = λ2y: Yongjin Li”. Thai Journal of Mathematics 8, no. 2 (August 1, 2010): 215–219. Accessed May 7, 2024. https://thaijmath2.in.cmu.ac.th/index.php/thaijmath/article/view/193.