Verdross, Alfred, The Status of Foreign Private Interests Stemming from Economic Development Agreements with Arbitration Clauses, in: The Southwestern Legal Foundation (ed.), Private Investors Abroad, Dallas 1964, Albany, NY 1965

Quasi-international agreements have their reason of validity in the general principle of law "pacta sunt servanda" and occasionally in other general principles of law, which the parties concurringly recognize as binding in entering into the agreement.