Roberto DK Liu, Laurien M Buffart*, Marie José Kersten, Marjolein Spiering, Johannes Brug, Willem van Mechelen and Mai JM Chinapaw
* Corresponding author: Laurien M Buffart l.buffart@vumc.nl
BMC Medical Research Methodology 2011, 11:30 doi:10.1186/1471-2288-11-30