Columbia subject headings:
Natural history.
Thoreau, Henry David, 1817-1862--Knowledge and learning.
Harvard subject headings:
Nature in literature.
Thoreau, Henry David, 1817-1862--Knowledge--Natural history.
Princeton subject headings:
Natural history--New England--History--19th century.
Nature in literature.
Thoreau, Henry David, 1817-1862--Knowledge--Natural history.