Columbia subject headings:
Inventions--History.
Technological innovations--History--20th century.
Technology--History--20th century.
Harvard subject headings:
Inventions--History--20th century.
Technological innovations--History--20th century
Technology--History--20th century
Princeton subject headings:
Inventions--History--20th century.
Technological innovations--History--20th century.
Technology--History--20th century.