Columbia subject headings:
Developing countries--Emigration and immigration--Economic aspects.
Emigration and immigration--Economic aspects.
Spain--Emigration and immigration--Economic aspects.
Harvard subject headings:
Developing countries--Emigration and immigration--Social aspects.
Emigration and immigration--Social aspects
Immigrants--Societies, etc.
Spain--Emigration and immigration--Social aspects.
Princeton subject headings:
Developing countries--Emigration and immigration--Economic aspects.
Emigration and immigration--Economic aspects.
Spain--Emigration and immigration--Economic aspects.