Ali Mohamad, Hussain, and Aqeel Falih Jaddoa. “Property of Oscillation of First Order Impulsive Neutral Differential Equations With Positive and Negative Coefficients”. Journal of Al-Qadisiyah for Computer Science and Mathematics, vol. 11, no. 1, Jan. 2019, pp. Math Page 45 - 51, doi:10.29304/jqcm.2019.11.1.457.