Columbia subject headings:
Canada--Relations--Mexico--Congresses.
Mexico--Relations--Canada--Congresses.
Harvard subject headings:
Canada--Foreign relations--1945---Congresses.
Canada--Relations--Mexico--Congresses.
Mexico--Foreign relations--1970-1988--Congresses.
Mexico--Relations--Canada--Congresses.
Princeton subject headings:
Canada--Relations--Mexico--Congresses.
Mexico--Relations--Canada--Congresses.