Franklin, W. S.; Stillman, M. H.; Sanford, R. L.; Warner, John A. C.; Sylvander, R. C. & Rounds, E. W. Aeronautic Instruments Section 4: Direction Instruments, report, 1923%; (https://digital.library.unt.edu/ark:/67531/metadc65778/m1/2/: accessed July 18, 2024), University of North Texas Libraries, UNT Digital Library, digital.library.unt.edu; .