Freeman, Major Marshall A. (5 April 1991). The Army Needs a Strategic Armored Gun System—Now!(PDF) (War College Individual Study Project). U.S. Army War College, Carlisle Barracks. pp. 12–14, 16. Archived(PDF) from the original on May 12, 2022. Retrieved 10 March 2022.
Freeman, Major Marshall A. (5 April 1991). The Army Needs a Strategic Armored Gun System—Now!(PDF) (War College Individual Study Project). U.S. Army War College, Carlisle Barracks. pp. 12–14, 16. Archived(PDF) from the original on May 12, 2022. Retrieved 10 March 2022.