Columbia subject headings:
Machine guns.
United States. Army--Procurement--History--19th century.
United States. Army--Procurement--History--20th century.
Harvard subject headings:
Machine guns.
United States. Army--Procurement--History--19th century.
United States. Army--Procurement--History--20th century.
Princeton subject headings:
Machine guns.
United States. Army--Procurement--History--19th century.
United States. Army--Procurement--History--20th century.