Balatta, S. A. ., I. . Hashim, E. S. . Ismail, O. . Bazighifan, and S. . Momani. “Fourth-Order Delay Differential Equations: New Monotonic Properties of Solutions”. Contemporary Mathematics, vol. 6, no. 1, Feb. 2025, pp. 1239-54, doi:10.37256/cm.6120255413.