Scholarly Books and Articles should be the heart of your research!
Books are a great place to get a wide range of knowledge about a country or area. They can provide background, analysis, data, and more.
Google Scholar is a great resource for finding scholarly resources. It is also a great place to check for the full-text of an article before submitting an ILL request.
Newspapers can be a great way to discover how an event was viewed internationally, especially things such as wars, elections, coups, debates, policies, etc.