Columbia subject headings:
Geology--New York (State)--Niagara Falls--Guidebooks.
Niagara Falls (N.Y. and Ont.)--Guidebooks.
Harvard subject headings:
Geology--Niagara Falls (N.Y. and Ont.)--Guidebooks.
Niagara Falls (N.Y. and Ont.)--Guidebooks.
Princeton subject headings:
Geology--Niagara Falls (N.Y. and Ont.)--Guidebooks.
Niagara Falls (N.Y. and Ont.)--Guidebooks.