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.
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.