Gordon, Sanford & Huff, Vearl N. Theoretical performance of liquid ammonia and liquid fluorine as a rocket propellant, report, July 3, 1953; (https://digital.library.unt.edu/ark:/67531/metadc53029/m1/1/: accessed December 11, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .