Value of Chromoendoscopy and Magnification Endoscopy in the Evaluation of Duodenal Abnormalities: a Prospective, Randomized Comparison - Kiesslich , R; Mergener , K; Naumann , C; Hahn , M; Jung , M; Koehler , H H; Nafe , B; Kanzler , S; Galle , P R (Endoscopy, 2003)