Columbia subject headings:
Harvard subject headings:
Human-machine systems--New York (State)--New York--History--20th century.
Subways--New York (State)--New York--History--20th century.
Urban transportation--New York (State)--New York--History--20th century.
Princeton subject headings:
Human-machine systems--New York (State)--New York--History--20th century.
Subways--New York (State)--New York--History--20th century.
Urban transportation--New York (State)--New York--History--20th century.