Nadeem Arshad, Muhammad, et al. “Antioxidant Potential of New Methyl-4-Hydroxy-2H- 1,2-Benzothiazine-3-Carboxylate-1,1-Dioxide Derivatives”. Asian Journal of Chemistry, vol. 23, no. 6, Mar. 2011, pp. 2801-5, https://asianpubs.org/index.php/ajchem/article/view/10501.