Columbia subject headings:
Africa--Emigration and immigration.
Africans--Developed countries.
Africans--Foreign countries.
Developed countries--Emigration and immigration.
Developing countries--Emigration and immigration.
Immigrants--Developed countries.
Working class--Developed countries.
Harvard subject headings:
Africa--Emigration and immigration.
Africans--Developed countries.
Developed countries--Emigration and immigration.
Developing countries--Emigration and immigration.
Foreign workers--Developed countries.
Princeton subject headings: