Authors: Gerdine A J Fransen; Corine J van Marrewijk; Suhreta Mujakovic; Jean W M Muris; Robert J F Laheij; Mattijs E Numans; Niek J de Wit; Melvin Samsom; Jan B M J Jansen; J André Knottnerus Journal: BMC Med Res Methodol Date: 2007-04-23 Impact factor: 4.615