Aqeel Ashraf, Muhammad, et al. “Synthesis, Spectral and Biological Studies of Transition Metal Complexes of 2-(4-Nitrophenylaminocarbonyl)benzoic Acid”. Asian Journal of Chemistry, vol. 23, no. 7, Mar. 2011, pp. 3117-20, https://asianpubs.org/index.php/ajchem/article/view/10553.