Carrigan, C.R.; Dunn, J.C. & Hardee, H.C. A Tool and a Method for Obtaining Hydrologic Flow Velocity Measurements in Geothermal Reservoirs, article, January 21, 1986; (https://digital.library.unt.edu/ark:/67531/metadc886194/m1/4/: accessed December 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .