Efficacy and safety of the dipeptidyl peptidase-4 inhibitor sitagliptin added to ongoing pioglitazone therapy in patients with type 2 diabetes: a 24-week, multicenter, randomized, double-blind, placebo-controlled, parallel-group study. - Rosenstock,J.; Brazg,R.; Andryuk,P.J. (Clin Ther, 2006)