Yang, Ting-Hai, et al. “Synthesis and Crystal Structure of 3D-Superamolecular Zinc Complex Derived from Pyridine-2,5-Dicarboxylate and Oxalate”. Asian Journal of Chemistry, vol. 25, no. 16, Oct. 2013, pp. 8946-8, doi:10.14233/ajchem.2013.14925.