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Add keywords. When they perform searches, databases will try to find articles that have all of the keywords you used in your search. The more keywords you use, the less likely it will be that there will be sources that have all of them, and the fewer results you'll get. Try to use between three and five keywords.
Use the search limiters on the left of the results list. These allow you to narrow your search results by date, type of publication, language, and many other characteristics. For example, if you only want to see books and articles about your topic, select the boxes for "Books" and "Academic Journals" under the "Source Types" option.
Take away keywords. When they perform searches, databases will try to find articles that have all of the keywords you used in your search. The fewer keywords you have, the more likely it will be that there will be sources that have all of them, and the greater number of results you'll get. Try to use between three and five keywords.
Use different keywords. Not all sources use the same words to describe the same thing. For example, one source might say "vaccine" where another says "immunization." By trying different keywords, you ensure that you find all sources on your topic.
Remove some search limiters, if you have them checked. If you have added too many limiters, there may be no sources that meet all of those criteria. You may need to remove some limiters to have a better chance of finding sources.