Treaties in Force (TIF)
Office of the Legal Advisor, U.S. Department of State, Treaty Affairs Staff. This publication lists bilateral and multilateral treaties and other international agreements of the United States on record in the Department of State as being in force as of January 1 of the specified year. This is an excellent resource to verify that the treaty you located in another resource is still in force in the United States.
United Nations Master Treaty Index on CD-ROM
United Nations (1995-current) - L1.
Worldwide Tax Treaty Index: 1997-98 Edition
Tax Analysts (1998) - UES