In basic terms, scholarly sources are written by scholars for scholars and go through a scholarly publication process. For journal articles, this scholarly publication process usually includes some form of peer-review, which means it is vetted by experts in the field and therefore considered more credible than information that hasn't gone through this process. Journal articles are the type of sources that are most likely to contain empirical evidence based on original studies conducted by the authors.
1. Don't search as a single phrase - instead, break your topic up into main concepts and place each concept on its own search line, separated by AND
2. Not finding enough sources? Think of synonyms for each of your concepts and combine them with ORS
3. Use truncations to include multiple variations of a word, i.e. persist* (includes persist, persistence, and persistent)
4. Use the Peer Reviewed or Scholarly Articles limiters in your search results