Fawzi AL-Azzawi, S., and K. A. Abed. “Using Δ - Discriminate Method to Determine the Stability and Bifurcation of Chen Chaotic System”. AL-Rafidain Journal of Computer Sciences and Mathematics, vol. 8, no. 2, Dec. 2011, pp. 111-22, doi:10.33899/csmj.2011.163646 .