Columbia subject headings:
Machine guns--History.
Military art and science--History.
War and society.
Harvard subject headings:
Machine guns--History.
Military art and science--History
Military history, Modern--19th century
Military history, Modern--20th century
Sociology, Military.
War and society.
Princeton subject headings:
Machine guns--History.
Military history, Modern--19th century.
Military history, Modern--20th century.
Sociology, Military.
War and society.