Columbia subject headings:
Geographers--United States--Biography--Congresses.
Geography--Congresses.
Sauer, Carl Ortwin, 1889-1975--Congresses.
Harvard subject headings:
Geographers--United States--Biography--Congresses.
Geography--Congresses
Sauer, Carl Ortwin, 1889-1975--Congresses.
Princeton subject headings:
Geographers--United States--Biography--Congresses.
Geography--Congresses.
Sauer, Carl Ortwin, 1889-1975--Congresses.