1. Cohen et al 1971"
2. Kirves 197323 Cohen;and, Rosenberg,1974
3. Nurse anaesthetists
4. anaesthesia Cohen et al 19806 400 Dental assistants, high exposure Lauwerys et;Physicians,1981
5. high exposure Heidam 1984'8 179 Dental assistants, private;workers;clinics