Columbia subject headings:
Chicle industry workers--Mexico--Campeche (State)--History--20th century.
Chicle industry--Mexico--Campeche (State)--History--20th century.
Harvard subject headings:
Chicle industry workers--Mexico--Campeche (State)--History--20th century.
Chicle industry--Mexico--Campeche (State)--History--20th century.
Princeton subject headings:
Campeche (Mexico : State)--Social life and customs.
Chicle industry--Mexico--Campeche (State).