H. M. Lotfy, M. A. M. Hegazy, and S. A. N. Abdel-Gawad, “Simultaneous determination of Simvastatin and Sitagliptin in tablets by new univariate spectrophotometric and multivariate factor based methods”, Eur. J. Chem., vol. 4, no. 4, pp. 414–421, Dec. 2013.