RT Journal Article SR Electronic T1 Peptic ulcer and non-steroidal anti-inflammatory agents JF Gut JO Gut FD BMJ Publishing Group Ltd and British Society of Gastroenterology SP 111 OP 111 DO 10.1136/gut.28.1.111 VO 28 IS 1 A1 R D Montgomery YR 1987 UL http://gut.bmj.com/content/28/1/111.1.abstract AB