Keywords may be separated by AND and/or OR statements for greater control of the search results.
For example, astronomy AND poster would generate a result set that contain both words. However, for astronomy OR poster, the result set returned would contain both or either words.
Exact matches can be searched for by enclosing keywords in double-quotes.
For example, "archaeology book" would generate a result set which match the exact string.
Brackets can be used for further control on the result set.
For example, astronomy and (book or stargazer or "created moon").