Combs, S. K.; Foust, C. R.; Fehling, D. T.; Gouge, M. J. & Milora, S. L. Repetitive, small-bore two-stage light gas gun, article, January 1, 1991; (https://digital.library.unt.edu/ark:/67531/metadc1057046/m1/1/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, digital.library.unt.edu; .