There are lots of helpful guides to researching public international law. The web sites and books listed on this page are a few of the most helpful.
International and Foreign Legal Research: A Coursebook, 2d ed.
by
Marci Hoffman & Mary Rumsey
International Legal Research in a Nutshell, 2d ed.
by
Marci B. Hoffman & Robert C. Berring
Guide to International Legal Research
by
George Washington Journal of International Law and Economics
Legal Research in a Nutshell, 14th ed.
by
Kent C. Olson
Fundamentals of Legal Research, 10th ed.
by
Steven M. Barkan, Barbara A. Bintliff & Mary Whisner
Contemporary Practice of Public International Law
by
Ellen G. Schaffer & Randall J. Snyder, eds.