Coronavirus disease outbreak: a simple infection prevention measure using a surgical mask during endoscopy - Maruyama, Hirotsugu; Higashimori, Akira; Yamamoto, Kei; Nakata, Akinobu; Ishikawa-Kakiya, Yuki; Yamamura, Masafumi; Fujiwara, Yasuhiro (Endoscopy, 2020)