Ümit Taş, Ewout W Steyerberg, Sita MA Bierma-Zeinstra, Albert Hofman, Bart W Koes and Arianne P Verhagen*
* Corresponding author: Arianne P Verhagen a.verhagen@erasmusmc.nl
BMC Geriatrics 2011, 11:22 doi:10.1186/1471-2318-11-22