United States. Government Accountability Office. Defense Acquisitions: Improved Management and Oversight Needed to Better Control DOD's Acquisition of Services, text, May 10, 2007; (https://digital.library.unt.edu/ark:/67531/metadc294731/m1/1/: accessed November 15, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .