Postoperative levonorgestrel-releasing intrauterine system for pelvic endometriosis-related pain: a randomized controlled trial - Tanmahasamut, P; Rattanachaiyanont, M; Angsuwathana, S; Techatraisak, K; Indhavivadhana, S; Leerasiri, P (Obstet Gynecol, 2012)