Durrani, Ayesha, et al. “Potentiometric Studies of Some Ternary System of Cu(II) Complexes With Picolinic Acid and Some Amino Acids”. Asian Journal of Chemistry, vol. 18, no. 4, Mar. 2010, pp. 3114-6, https://asianpubs.org/index.php/ajchem/article/view/20763.