RT Journal Article SR Electronic T1 DUPLICATION OF THE MITRAL VALVE JF British Heart Journal JO Heart FD BMJ Publishing Group Ltd and British Cardiovascular Society SP 296 OP 300 DO 10.1136/hrt.19.2.296 VO 19 IS 2 A1 E. D. Wigle YR 1957 UL http://heart.bmj.com/content/19/2/296.abstract AB