MANDAL, U., and T.K. PAL. “Sustained Release of Metformin HCl from Hydroxy Propyl Methyl Cellulose Matrices: Formulation and in Vitro Evaluation”. Asian Journal of Chemistry, vol. 20, no. 2, Mar. 2010, pp. 1163-74, https://asianpubs.org/index.php/ajchem/article/view/12499.