Borkowski, C. J.; Dandl, R. A.; Epler, E. P. & Harrill, C. S. Instrumentation and Controls Division Annual Progress Report for the Period Ending September 1, 1966, report, June 1967; (https://digital.library.unt.edu/ark:/67531/metadc100300/m1/1/: accessed April 23, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; .