Hajian, R., et al. “Combination of Ratio Derivative Spectrophotometry With Simultaneous Standard Additions Method for Determination of Sulfamethoxazole and Trimethoprim”. Asian Journal of Chemistry, vol. 22, no. 8, June 2010, pp. 6569-7, https://asianpubs.org/index.php/ajchem/article/view/11853.