Every source contains rich clues to other useful sources. It’s a treasure map that can lead you to sources you would never find by pure searching. This skill can help you discern a conversation occurring among a set of scholars or writers about your topic. Think of each good source as giving clues along two axes:

• Forward and backward in time. If you look at a source and see in its bibliography that there are fifty references, you can do a quick scan of the titles and authors to look for other sources you might investigate. These previously cited sources give you a rough map of how the topic has been researched to that point. Similarly, you can look at the “cited by” feature within a database (or Google Scholar) to look for other sources who are continuing the conversation and cited your source.
• Side to side across the scholarly conversation. When looking at a source you like, collect key terms, phrases, and names to find other sources that are similar. These other keywords can lead to other types of evidence and examples that offer more coverage of your topic.

Subject Headings

Most databases will include related subject headings alongside each search result. Subject headings are a form of descriptive metadata. At their simplest they may be tags chosen by the authors, but most databases use a controlled vocabulary assigned by professional catalogers

The advantage of controlled subject terms is that they’re standardized terms which will be assigned to all appropriate content no matter what terminology (or even language) is used by the author. For example, the database Academic Search Complete uses the subject term “motion pictures,” even if the article uses the words “films,” “movies,” or “cinema.”

Whenever you find a good article in a database, check out the subject headings. If one or more of them look like matches for your topic, re-run your search using those terms—and be sure to specify you want those terms in the subject field. That will ensure the search results are really about that subject and don’t just happen to mention those words in passing somehow.

Will you find the “perfect” source?

One last tip for your research is to keep an open mind. If you are not finding good sources, don’t get discouraged. Try a different combination of keywords, synonyms, or ask your librarian or professor for help. You don’t need a “perfect” source that aligns with your paper. You can take small bits of information from multiple sources and combine them into your own argument.