Arango, E. F., F. A. Patiño, M. A. Quintero, and M. M. Arenas. “Levels of Physical Activity, Barriers, and Stage of Change in an Urban Population from a Municipality in Colombia”. Colombia Medica, vol. 42, no. 3, Sept. 2011, pp. 352-61, doi:10.25100/cm.v42i3.882.