TY - JOUR T1 - Tips for learners of evidence-based medicine: 4. Assessing heterogeneity of primary studies in systematic reviews and whether to combine their results JF - Canadian Medical Association Journal JO - CMAJ SP - 661 LP - 665 DO - 10.1503/cmaj.1031920 VL - 172 IS - 5 AU - Rose Hatala AU - Sheri Keitz AU - Peter Wyer AU - Gordon Guyatt A2 - , Y1 - 2005/03/01 UR - http://www.cmaj.ca/content/172/5/661.abstract ER -