RT Journal Article SR Electronic T1 Imperfect measure of hospital safety JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP E451 OP E452 DO 10.1503/cmaj.109-4186 VO 184 IS 9 A1 Vogel, Lauren YR 2012 UL http://www.cmaj.ca/content/184/9/E451.abstract