Use
Boolean Operators:
and -
combines search terms so that each search result contains all of the terms. For
example, immunization and infant finds articles that contain both "immunization" and "infant."
or -
combines search terms so that each search result contains at least one of the
terms. For example, shots or vaccinations finds results that contain either "shots" or "vaccinations."
not - excludes
terms so that each search result does not contain any of the terms that follow
it. For example, shots not guns finds results that contain "shots" but
not "guns."