Long-term safety and efficacy of empagliflozin, sitagliptin, and metformin: an active-controlled, parallel-group, randomized, 78-week open-label extension study in patients with type 2 diabetes - Ferrannini, E; Berk, A; Hantel, S; Pinnetti, S; Hach, T; Woerle, H J; Broedl, U C (Diabetes Care, 2013)