Travaux préparatoires are the preparatory documents used to build a treaty. They are sometimes used in the interpretation of a treaty. Travaux préparatoires may include being published in a book-format or as preliminary drafts or records of international conferences.
Contemporary Issues in International Arbitration and Mediation by 
Commentary on the 1969 Vienna Convention on the Law of Treaties by 
Treaty Interpretation and the Vienna Convention on the Law of Treaties - 30 Years On by When citing international material such as treaties or UN documents follow the guidance of the AGLC starting on page 121. For foreign domestic materials such as cases and legislation see the examples starting on page 197.
See Victoria University's guide on Frequently Cited Treaties for examples.
If you are preparing material for a Jessup Moot, they have a set of official rules on citation systems used. Amongst others, citation systems include:
Google Scholar allows you to search for scholarly literature such as journal articles, books and theses across different academic disciplines.
Note that not all information on Google Scholar is freely accessible.
International Criminal Justice and the Politics of Compliance by 
The Principle of Complementarity in International Criminal Law by 
Foundations of international criminal law by 
Unifying and Harmonizing Substantive Law and the Role of Conflict of Laws by 
The International Law of the Sea by 
Core documents on international law by 
The Cambridge Companion to International Law by 
International law : contemporary principles and practices by 
Parry and Grant Encyclopaedic Dictionary of International Law by 
