1. Finnish Institute of Occupational Health; Cochrane Work Review Group; PO Box 310 Kuopio Finland 70101
2. Finnish Institute of Occupational Health; Topeliuksenkatu 41 b Helsinki Finland
3. Finnish Institute of Occupational Health; Cochrane Work Review Group; Topeliuksenkatu 41 aA Helsinki Finland FI-00250
4. University of Iowa Hospitals and Clinics; C512 GH, 200 Hawkins Drive Iowa City IA USA 52241
5. Finnish Institute of Occupational Health; P.O.Box 486 Tampere Finland FI-33101
6. Centers for Disease Control and Prevention (CDC); National Personal Protective Technology Laboratory (NPPTL), National Institute for Occupational Safety and Health (NIOSH); 626 Cochrans Mill Road Pittsburgh PA USA 15236