Columbia subject headings:
Harvard subject headings:
Civil unions--Law and legislation--Europe--Congresses.
Gay couples--Legal status, laws, etc.--Europe--Congresses.
Same-sex marriage--Law and legislation--Europe--Congresses.
Princeton subject headings:
Gay adoption--Government policy--European Union countries.
Gay couples--Legal status, laws, etc.--European Union countries.
Gay rights--European Union countries.
Gays--Legal status, laws, etc.--European Union countries.
Homosexuality--Law and legislation--European Union countries.
Same-sex marriage--Law and legislation--European Union countries.