School of Public Health and Tropical Medicine, James Cook University, Townsville, Queensland, Australia
Received August 11, 1999; accepted November 1, 1999.
Address correspondence and reprint requests to B. F. Walker, D.C., M.P.H., School of Public Health and Tropical Medicine, James Cook University, Anton Breinl Centre, Townsville General Hospital, Eyre Street, Townsville, Queensland, 4810 Australia. E-mail: [email protected]