Oxford Bibliographies Online - International Law. Provides authoritative encyclopaedic entries and annotated bibliographies on a range of topics such as General Customary Law and General Principles of Law.
Max Planck Encyclopedia of Public International Law. Contains comprehensive and authoritative overviews of all aspects of international law. Entries are arranged alphabetically by topic under broad subjects such as Sources of International Law, Customary International Law, General Principles of International Law, State Practice and the Law of Treaties.
The following resources provide article-by-article commentary on all 128 Articles of the Rome Statute. They include relevant case law and academic commentary: