F. Khan, M. S. M. I. Razzak, M. Z. R. Khan, K. R. Azam, S. M. A. Sadat, and M. S. Reza, “Preparation and <i>In vitro</i> Evaluation of Theophylline Loaded Gastroretentive Floating Tablets of METHOCEL K4M”, Dhaka Univ. J. Pharm. Sci, vol. 7, no. 1, pp. 65–70, Oct. 2008.