HOWARD, D. W.; WILLMS, R. S. & BIRDSELL, S. A. TESTING OF A PRACTICAL LOW PRESSURE PERMEATOR, article, November 1, 1999; (https://digital.library.unt.edu/ark:/67531/metadc725017/m1/1/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, digital.library.unt.edu; .