1. Bindman, A. B., Grumbach, K., Keane, D., & Lurie, N. (1993). Collecting data to evaluate the effect of health policies on vulnerable populations. Family Medicine, 25, 114–119.
2. Canavan, R., Barry, M. M., Matanov, A., Barros, H., Gabor, E., Greacen, T., et al. (2012). Service provision and barriers to care for homeless people with mental health problems across 14 European capital cities. BMC Health Services Research, 12, 222.
3. Conover, S., Berkman, A., Gheith, A., Jahiel, R., Stanley, D., Geller, P. A., et al. (1997). Methods for successful follow-up of elusive urban populations: an ethnographic approach with homeless men. Bulletin of the New York Academy of Medicine, 74, 90–108.
4. Doherty, S. T., Lemieux, C. J., & Canally, C. (2014). Tracking human activity and well-being in natural environments using wearable sensors and experience sampling. Social Science and Medicine, 106, 83–92.
5. Duncan, M. J., Mummery, W. K., & Dascombe, B. J. (2007). Utility of global positioning system to measure active transport in urban areas. Medicine & Science in Sports & Exercise, 39, 1851–1857.