Precup, Radu. “Convexity and Quadratic Monotone Approximation in Delay Differential Equations”. Rev. Anal. Numér. Théor. Approx. 30, no. 1 (February 1, 2001): 89–93. Accessed April 8, 2025. https://ictp.acad.ro/jnaat/journal/article/view/2001-vol30-no1-art12.