- Dr E Hnizdo, National Institute for Occupational Safety and Health, 1095 Willowdale Road, MS PB 163, Morgantown, WV 26505, USA
- Received May 5, 1999
- Revision requested June 21, 1999
- Revised July 28, 1999
- Accepted September 6, 1999
- First published January 1, 2000.
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