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van Walraven CV, Paterson JM, Kapral M, Chan B, Bell M, Hawker G, Gollish J, Schatzker J, Williams JI, Naylor CD.van Walraven CV, et al.CMAJ. 1996 Sep 15;155(6):697-706.CMAJ. 1996.PMID: 8823215Free PMC article.