Columbia subject headings:
Harvard subject headings:
Catskill Aqueduct (N.Y.)
Geology--New York (State)
Princeton subject headings:
Catskill Aqueduct (N.Y.)
Geology--Hudson River Valley (N.Y. and N.J.).
Geology--New York (State)--Catskill Mountains.
Geology--New York (State)--Croton River Valley.
Geology--New York (State)--New York (State)--New York.