Basic epidemiology Beaglehole R, Bonita R and Kjellstrom T. WHO 1993

Guidelines for safe recreational - water environments Vol 2: swimming pools, spas and similar recreational- water environments. WHO/SDE/WSH/00.6 2000

Risk assessment's   webpages:
www.epa.gov/ncea/risktool.htm
www.epa.gov/ncea/exposure.htm