Mace, R.E., Chowdhury, A.H., Anaya, R., Way, S.(2000).

Groundwater availability of the Trinity Aquifer, hill country area, Texas: Numerical Simulations through 2050.Texas Water Development Board. September.[A report detailing the Trinity Aquifer numerical simulations to find the groundwater availability through 2050.]

http://www.eardc.txstate.edu/EA-hydrogeology.html.Edwards Aquifer Research Center.[The site gives an description of Edwards Aquifer Hydrogeologic formations.]

http://tx.cr.usgs.gov/reports/wrir/94/4039/html/4039.html USGS.Geologic History and Hydrogeologic Setting of the Edwards-Trinity Aquifer System, West-Central Texas.[A report on the hydrogeologic setting of the Edwards-Trinity Aquifer]

http://www.redrival.com/bexar/triaq.html.San Antonio Water Supply.

http://quickfacts.census.gov/qfd/states/48/48453.html. The United States Census Bureau, provides numerical data for all the states and counties in the USA.