TY - JOUR T1 - The two-step to two-tier JF - Canadian Medical Association Journal JO - CMAJ SP - 541 LP - 541 DO - 10.1503/cmaj.1041347 VL - 171 IS - 6 A2 - , Y1 - 2004/09/14 UR - http://www.cmaj.ca/content/171/6/541.abstract ER -