United States. Government Accountability Office. Private Pensions: Airline Plans' Underfunding Illustrates Broader Problems with the Defined Benefit Pension System, text, October 7, 2004; (https://digital.library.unt.edu/ark:/67531/metadc295080/m1/1/: accessed March 22, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .