S. G. Trost, N. Owen, A. E. Bauman, J. F. Sallis, and W. Brown, ′′Correlates of adults' participation in physical activity: review and update,′′ Medicine and Science in Sports and Exercise, vol.34, no.12, pp.1996-2001, 2002.
N. Humpel, N. Owen, and E. Leslie, ′′Environmental factors associated with adults' participation in physical activity - A review,′′ American Journal of Preventive Medicine, vol.22, no.3, pp.188-199, 2002.