PT - JOURNAL ARTICLE AU - T. W. Anderson AU - M. J. Ashley AU - A. E. Clarke TI - Letter: The retrospective study DP - 1976 Jan 10 TA - Canadian Medical Association Journal PG - 13b--13 VI - 114 IP - 1 4099 - http://www.cmaj.ca/content/114/1/13b.short 4100 - http://www.cmaj.ca/content/114/1/13b.full SO - CMAJ1976 Jan 10; 114