- Correspondence to Dr P van Vliet, Leiden University Medical Center, Department of Gerontology and Geriatrics (C2-R), PO Box 9600, 2300 RC, Leiden, The Netherlands;
- Received May 4, 2009
- Revised December 28, 2009
- Accepted January 16, 2010
- First published June 11, 2010.
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