Leonardo, L. R., Crisostomo, B. A., Solon, J. A. A., Rivera, P. T., Marcelo, A. B., & Villasper, J. M. (2007). Geographical information systems in health research and services delivery in the Philippines. Geospatial Health, 1(2), 147–155. https://doi.org/10.4081/gh.2007.263