TY - JOUR T1 - Letter: Interpretation of PPD skin test JF - Canadian Medical Association Journal JO - CMAJ SP - 816b LP - 816 VL - 113 IS - 9 AU - J. H. Joncas Y1 - 1975/11/08 UR - http://www.cmaj.ca/content/113/9/816b.abstract ER -