Difficult Biliary Stones in the Elderly: Endoscopic Retrograde Cholangiography. A Single Surgical Tertiary Center Experience With Follow Up - Antypas, P; Cereatti, F; Fiocca, F; Cappello, A; Eberspacher, C; Fanello, G; Mascagni, D; Donatelli, G (Endoscopy, 2021)