Koppenjan, S.K.; Allen, C.M.; Gardner, D. & Wong, H.R. A lightweight ground penetrating radar, article, December 31, 1998; (https://digital.library.unt.edu/ark:/67531/metadc688343/m1/1/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, digital.library.unt.edu; .