Endoscopic mucosal resection under gel immersion for superficial nonampullary duodenal epithelial neoplasms - Yachida, Tatsuo; Kobara, Hideki; Tada, Naoya; Nishiyama, Noriko; Takata, Tadayuki; Masugata, Hisashi; Masaki, Tsutomu (Endoscopy, 2021)