S. K. Dawood, I. A. Hassen, and T. Y. Yousif, “Synthesis and Characterization of Tetradentat Macrocyclic Ligands and its Complexes with Mn(II),Fe(II),Co(II),Ni(II) and Cu(II) Metal Ions”, EDUSJ, vol. 18, no. 2, pp. 1–10, Jun. 2006.