QUALITY OF COLONOSCOPY «QUACOL». THE RESULTS OF THE PROSPECTIVE MULTICENTRE STUDY «QUACOL 2» COMPARED WITH RESULTS OF THE «QUACOL 1» STUDY IN RUSSIA - Kashin, S; Nikonov, E; Nekhaykova, N; Veselov, V; Veselov, A; Galkova, Z; Lileev, D; Korolev, M; Starkov, Y; Repici, A; Hassan, C (Endoscopy, 2020)