Publication date 1986-12-00 Published date 22/02/2016 Last updated 22/02/2016 Download the file ChJul80.1024.8196.000.003.Jul1980.8.pdf(614.18 KB) Related Collections from the Archive Epidemiology: how to do a studyDISA Archive Related content DISA ArchiveSourceCritical Health Number 18 December 1986