Y. AL-Bayati, A., K. K. Abbo, and A. J. S. “Generalized CG-Algorithms Based on Rational Sigmoid Model for Unconstrained Optimization”. IRAQI JOURNAL OF STATISTICAL SCIENCES, vol. 10, no. 1, June 2010, pp. 123-36, doi:10.33899/iqjoss.2010.030495.