Back complaints in the elders (BACE); design of cohort studies in primary care: an international consortium.
Scheele J, Luijsterburg PA, Ferreira ML, Maher CG, Pereira L, Peul WC, van Tulder MW, Bohnen AM, Berger MY, Bierma-Zeinstra SM, et al. BMC Musculoskelet Disord. 2011 Aug 19; 12:193. Epub 2011 Aug 19.