RT Journal Article SR Electronic T1 The Cochrane Collaboration celebrates 20 years JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP 1162 OP 1163 DO 10.1503/cmaj.131213 VO 185 IS 13 A1 Alan Cassels YR 2013 UL http://www.cmaj.ca/content/185/13/1162.abstract