RETRACTED: Cardiovascular and mortality outcomes of DPP-4 inhibitors vs. sulfonylureas as metformin add-on therapy in patients with type 2 diabetes: A systematic review and meta-analysis - Refli Hasan; Uliana Y. Chugaeva; Mahdi Mohammadian; Somayeh Zamanifard; Abdollah Mohammadian-Hafshejani (PLoS ONE, 2025)