Coles, Willard D. & Callaghan, Edmund E. Full-Scale Investigation of Several Jet-Engine Noise-Reduction Nozzles, report, January 1, 1958; (https://digital.library.unt.edu/ark:/67531/metadc60812/m1/1/: accessed October 17, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .