TY - JOUR T1 - Is the WHO analgesic ladder still valid? JF - Canadian Family Physician JO - Can Fam Physician SP - 514 LP - 517 VL - 56 IS - 6 AU - Grisell Vargas-Schaffer Y1 - 2010/06/01 UR - http://www.cfp.ca/content/56/6/514.abstract N2 - ER -