1. University of Bologna; Department of Medical and Surgical Sciences; UO Medicina del Lavoro - Policlinico Sant'Orsola-Malpighi Via Palagi 9 Bologna Italy 40138
2. Finnish Institute of Occupational Health; P.O.Box 486 Tampere Finland FI-33101
3. Free University Medical Centre; De Boelelaan 1117 Amsterdam Netherlands 1081 HZ
4. University of Antwerp; Epidemiology and Social Medicine; Universiteitsplein 1 Antwerpen Belgium 2610
5. Institut de Veille Sanitaire; Département Santé Travail; 12, rue du val d'Osne Saint Maurice France 94415