Mohammad, Mohammad Abdul-Azim, et al. “Development and Validation of a Reversed-Phase Column Liquid Chromatographic Method for Simultaneous Determination of Two Novel Gliptins in Their Binary Mixtures With Metformin”. European Journal of Chemistry, vol. 3, no. 2, June 2012, pp. 152-5, doi:10.5155/eurjchem.3.2.152-155.570.