Columbia subject headings:
Harvard subject headings:
Papaloapan River Valley (Mexico)--Colonization.
Papaloapan River Valley (Mexico)--Economic conditions.
Papaloapan Valley--Colonization.
Papaloapan Valley--Economic conditions.
Princeton subject headings:
Papaloapan River Valley (Mexico)--Colonization.
Papaloapan River Valley (Mexico)--Economic conditions.