Reference sources, such as dictionaries and encyclopedias, can provide valuable background information about your topic. These sources will be useful for refining your research and coming up with keywords to use when searching. Some of entries will contain bibliographies which you can use to locate key books and articles on your topic.
Articles published in Annuall Reviews provide reviews of the literature that has been published on topics from different academic disciplines. If you find an article related to your research, it can be a great starting point because it will provide an overview of the literature and a bibliography of sources.