Sheahan, J. E.; Ewing, R. D. & Ewing, S. K. Willamette Oxygen Supplementation Studies: Ammonia Analysis and Adult Returns: Annual Report 1994., report, September 1, 1995; (https://digital.library.unt.edu/ark:/67531/metadc669985/m1/1/: accessed August 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .