M. D. Kiran and B. N. Naik, “A clinical study to determine metformin as a cause of serum vitamin B12 decrease and effect of combination of metformin and mecobalamin on serum vitamin B12 levels in type 2 diabetics”, Int J Basic Clin Pharmacol, vol. 6, no. 5, pp. 1066–1072, Apr. 2017.