Kempen G I J M, Oude Wesselink S F, van Haastregt J C M, Zijlstra G A R
CAPHRI School for Public Health and Primary Care, Department of Health Services Research, Maastricht University, The Netherlands.
Age Ageing. 2011 Jul;40(4):519-23. doi: 10.1093/ageing/afr041. Epub 2011 May 7.