Al-Issa, Mahmoud A., et al. “Synthesis and Characterization of Schiff Base Derived From Chitosan and Its Complexes With (Co+2, Ni+2 and Cu+2)”. Ibn AL-Haitham Journal For Pure and Applied Sciences, vol. 29, no. 2, Mar. 2017, pp. 115-29, https://jih.uobaghdad.edu.iq/index.php/j/article/view/90.