SH, Zaineb . Hamed, and Fadhel F S. 2011. “VARIATIONAL FORMULATION OF NONLINEAR ORDINARY DELAY DIFFERENTIAL EQUATIONS”. Journal of Al-Qadisiyah for Computer Science and Mathematics 3 (1):Math Page 314– 325. https://doi.org/10.29304/jqcm.2011.3.1.703.