Columbia subject headings:
Cocoa trade--Nigeria.
Yoruba (African people)--Economic conditions.
Yoruba (African people)--Social conditions.
Harvard subject headings:
Cocoa trade--Nigeria.
Yoruba (African people)--Economic conditions.
Yoruba (African people)--Social conditions.
Princeton subject headings:
Cocoa trade--Nigeria.
Yoruba (African people)--Economic conditions.
Yoruba (African people)--Social conditions.