The databases simply match the words you enter in the search box. Not all authors use the same language to describe similar topics, so you will need to try a variety of searches.
Examples
Using AND, OR, and NOT with keywords can help broaden or narrow your search.
AND | OR | NOT |
joins dissimilar terms; helps narrow your search Example college AND "social mobility" |
joins similar terms; helps broaden your search Example colleges OR universities |
excludes terms; helps narrow your search Example college NOT "graduate students" |
The asterisk * is the most common truncation symbol.
You do have to be careful because you might get unexpected results.