Using the sources you have to locate more
When you find a few relevant articles or books, use what you have found to find more sources for your research.
Use tools in the database
In most of Milne's databases, you'll see a Cited By or References link as part of search results. Looking at other works citing the ones you've already found can help you find additional relevant materials.
Use Bibliographies and References
Browse the bibliography or references at the end of a relevant book, article, or entry in a reference work:
Use Scopus to find more information about the sources cited in an article you are using. Scopus can connect you to other articles like yours. Use this to find how many times your article was cited, read the articles related to yours, and find out what other works the authors of your source have published.
Use Google Scholar to find out who cited the relevant work: