411 REFERENCE · Wikibooks
How To Search/Boolean Logic
Reference material by Wikibooks contributors. This retains its source identity and is not 411 news reporting.
Boolean logic symbolically represents relationships between entities. There are three Boolean operators:
AND
Use the AND operator to retrieve a set in which each citation contains all the search terms. This operator places no condition on where the terms are found in relation to one another; the terms simply have to appear somewhere in the same citation.
OR
Use the OR operator to retrieve documents that contain at least one of the specified search terms.
Use OR when you want to pull together articles on similar subjects.
NOT
Use the NOT operator to exclude the retrieval of terms from your search.
Sources
Originally copied from PubMed Tutorial.
See also
Wikipedia Articles:
http://en.wikipedia.org/wiki/Boolean_algebra
http://en.wikipedia.org/wiki/Logical_operator
http://en.wikipedia.org/wiki/Venn_diagram