United States. War Department.Browning machine gun caliber .50, M2, aircraft, fixed and flexible.,
book,
April 30, 1942;
Washington D.C..
(https://digital.library.unt.edu/ark:/67531/metadc29988/m1/60/:
accessed May 23, 2024),
University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu;
crediting UNT Libraries Government Documents Department.