SINGLE-OPERATOR PERORAL CHOLANGIOSCOPY-GUIDED LITHOTRIPSY FOR DIFFICULT BILIARY STONES - A PROSPECTIVE MULTICENTER STUDY - Moreira, M; Costa, D; Alexandrino, G; Fernandes, J; Araújo, T; Lourenço, L; Campos, S; Horta, D; Bana e Costa, Tiago; Lopes, Luís; Canena, Jorge (Endoscopy, 2020)