Search TGH Explanations & Help:

Query Language
The text search engine allows queries to be formed from arbitrary Boolean expressions containing the keywords AND, OR, and NOT, and grouped with parentheses. For example:

information retrieval

finds documents containing 'information' or 'retrieval'

information or retrieval
same as above

information and retrieval
finds documents containing both 'information' and 'retrieval'

information not retrieval
finds documents containing 'information' but not 'retrieval'

(information not retrieval) and WAIS
finds documents containing 'WAIS', plus 'information' but not 'retrieval'

web*
finds documents containing words starting with 'web'