The Statute of the International Court of Justice, Article 38, lays out the basic sources of international law:
In additional to searching Lexis+ and Westlaw for articles on FCIL topics published in US law reviews, be sure to look at these specialized databases:
Oxford bibliographies. International LAw by 
Basic Documents in International Law by
Basic Documents in International Law draws together all of the most important documents needed for the study of international law. Collated by Ian Brownlie, a worldwide expert in the field, this book has provided students and practitoners with the most essential instruments giving a thorough grounding in this diverse and fascinating field of law.
International Law by
Encompassing the leading principles, practice and cases, and retaining and developing the detailed references which encourage and assist the reader in further study, this new edition motivates and challenges students and professionals while remaining accessible and engaging.
International Law by
The book explores the scope and function of international law, and explains how it helps to underpin our international political and economic systems. It then goes on to examine the wider theoretical implications of international law's role in modern society, including issues such as the independence of states, limits of national freedom of choice, human rights, and international crime.
Oppenheim's International Law by
First published in 1905/6 International Law or Oppenheim's International Law as it is widely known, has established itself as one of the number one reference volumes in the field of International Law.