Columbia subject headings:
Harvard subject headings:
Emigration and immigration--Government policy
Emigration and immigration--Government policy--Case studies.
Ports of entry--Security measures--Case studies.
Ports of entry--Security measures.
Princeton subject headings:
Case studies.
Emigration and immigration--Government policy--Case studies.
Emigration and immigration--Government policy.
Ports of entry--Security measures--Case studies.
Ports of entry--Security measures.