The Five College Library Catalog: Use keyword searching to search a phrase or combine terms (using and, or), or search with Subject Headings such as these:

Refugees - [country]
Refugees - Government policy - [country]
Asylum, right of - [country]
Internally displaced persons - [country or region]
Emigration and immigration
Forced labor
Forced migration
Human smuggling
Human trafficking - [country]
Minorities
Refugee camps
Return migration
Repatriation
War relief

Environmental refugees
Climatic changes - Social aspects
Global warming - Political aspects
Disaster relief - Political aspects
Floods - Colombia
Privatization - Law and legislation
Right to water
Afghanistan - History - Soviet occupation, 1979-1989
Refugees - Afghanistan
Bangladesh - History - Revolution, 1971-
War victims - Bangladesh
Burma - Ethnic relations
Karen (Southeast Asian people) - Burma
Human security - Africa
Women and war
Women refugees
Refugees - China - Hong Kong
Refugees - [country] - Medical care
Refugees - Health and hygiene
Refugees, Palestinian Arab - Lebanon
Refugees - Syria
Rwandans - Congo (Democratic Republic) - Goma (Nord-Kivu)

A keyword search can combine concepts:  nigeria* and (idp* or "internally displaced)