United States. Government Accountability Office. Highway Bridge Program: Clearer Goals and Performance Measures Needed for a More Focused and Sustainable Program, report, September 10, 2008; (https://digital.library.unt.edu/ark:/67531/metadc295800/m1/1/: accessed April 22, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .