Kucuk, Aysel, and Yucel Kadioglu. “Determination of Tramadol Hydrochloride by Using UV and Derivative Spectrophotometric Methods in Human Plasma”. Asian Journal of Chemistry, vol. 23, no. 2, Oct. 2010, pp. 663-7, https://asianpubs.org/index.php/ajchem/article/view/15839.