United States. Office of the Federal Register. Federal Register, Volume 74, Number 33, February 20, 2009, Pages 7777-7992, periodical, February 20, 2009; (https://digital.library.unt.edu/ark:/67531/metadc132895/m1/1/: accessed April 19, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .