Measures to prevent international terrorism which endangers or takes innocent human lives or jeopardizes fundamental freedoms and study of the underlying cause of those forms of terrorism and acts of violence which lie in misery, frustration, grievance and despair and which cause some people to sacrifice human lives, including their own, in an attempt to effect radical changes : letter dated 22 November 1972 from the Permanent Representative of the Democratic Yemen to the United Nations addressed to the Secretary-General