1. Centers for disease control and prevention. http://www.cdc.gov/asthma. Centers for disease control and prevention. http://www.cdc.gov/asthma.
2. National centers for environmental information and the national oceanic and atmospheric administration. http://www.ncdc.noaa.gov/cdo-web. National centers for environmental information and the national oceanic and atmospheric administration. http://www.ncdc.noaa.gov/cdo-web.
3. Openlayers. http://openlayers.org/. Openlayers. http://openlayers.org/.
4. pgrouting. http://pgrouting.org. pgrouting. http://pgrouting.org.