United States. Office of the Federal Register. Federal Register, Volume 74, Number 80, April 28, 2009, Pages 19125-19370, periodical, April 28, 2009; (https://digital.library.unt.edu/ark:/67531/metadc132942/m1/1/: accessed March 21, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .