RT Journal Article SR Electronic T1 The study of NOELs JF Canadian Medical Association Journal JO CMAJ FD Canadian Medical Association SP 1539 OP 1540 DO 10.1503/cmaj.1050011 VO 172 IS 12 A1 Catherine Collins YR 2005 UL http://www.cmaj.ca/content/172/12/1539.2.abstract