Mobinikhaledi, A., et al. “Synthesis of Some Novel Methyl- and Ethyl- 2-Aminothiophene-3-Carboxylate and Related Schiff-Bases”. Asian Journal of Chemistry, vol. 22, no. 9, July 2010, pp. 7399-04, https://asianpubs.org/index.php/ajchem/article/view/11996.