1. Leiden University Medical Center; Department of Public Health and Primary Care; PO Box 9600 Leiden Netherlands 2300 RC
2. RTI International; 3040 Cornwallis Road Research Triangle Park NC USA 27709-2194
3. 788 8th Avenue San Francisco California USA 94118
4. RAND; Statistics Group; P.O. Box 2138 M23-C Santa Monica CA USA 90407-2138
5. RAND Corporation; 1700 Main Street Santa Monica California USA 90406-2138