Cai B, Katz L, Alexander CM, Williams-Herman D, Girman CJ. Characteristics of patients prescribed sitagliptin and other oral antihyperglycaemic agents in a large US claims database. Int J Clin Pract. 2010 Nov;64(12):1601–8. doi: 10.1111/j.1742-1241.2010.02516.x. PMID: 20946268.