Gandhimathi, M., and T.K. Ravi. “RP-HPLC and HPTLC Estimation of Tramadol Hydrochloride and Paracetamol in Combination”. Asian Journal of Chemistry, vol. 20, no. 6, Mar. 2010, pp. 4940-2, https://asianpubs.org/index.php/ajchem/article/view/19124.