Columbia subject headings:
Environmental protection--Hudson River Valley (N.Y. and N.J.)
Environmentalism--Hudson River Valley (N.Y. and N.J.)--History.
Hudson River Valley (N.Y. and N.J.)--Environmental conditions.
Harvard subject headings:
Environmental protection--Hudson River Valley (N.Y. and N.J.)
Environmentalism--Hudson River Valley (N.Y. and N.J.)--History.
Hudson River Valley (N.Y. and N.J.)--Environmental conditions.
Princeton subject headings:
Environmental protection--Hudson River Valley (N.Y. and N.J.).
Environmentalism--Hudson River Valley (N.Y. and N.J.)--History.
Hudson River Valley (N.Y. and N.J.)--Environmental conditions.