Analgesic effectiveness of wound infiltration with bupivacaine versus a mixture of bupivacaine and tramadol for postoperative pain management among parturients undergoing elective cesarean section under spinal anesthesia: A randomized controlled trial - Mesay Milkias; Semagn Mekonnen; Hailemariam Getachew; Hailemariam Mulugeta; Siraj Ahmed; Melkamu Kebede; Belete Destaw; Medhanit Melese; Zemedu Aweke (PLoS ONE, 2025)