Diaguila, Anthony J.; Livingood, John N. B. & Eckert, Ernst R. G. Study of ram-air heat exchangers for reducing turbine cooling-air temperature of a supersonic aircraft turbojet engine, report, August 3, 1956; (https://digital.library.unt.edu/ark:/67531/metadc62770/m1/1/: accessed December 18, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .