Martin, R.J.; Boyd, P.J.; Noel, J.S. & Price, R.H. Bulk and mechanical properties of the Paintbrush tuff recovered from borehole USW NRG-6: Data report, report, November 1, 1994; (https://digital.library.unt.edu/ark:/67531/metadc690337/m1/1/: accessed December 10, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .