Boolean Search Operators
Boolean operators are placed between search terms to narrow or broaden the coverage of a search. Always include Boolean operators when you use more than one word or phrase as search terms.
AND
Helps to narrow and focus a search and increase the relevance of your results
The AND operator tells the database that all search terms linked with AND must be present in every hit within your search results. The terms may or may not be included in a phrase. Linking several terms with the AND operator will reduce the number of results by making the search increasingly specific, and will hopefully increase the relevance of the results.
Example: if you want to find references about synthesis especially concerned with riboflavin and the xylene ring, type synthesis AND riboflavin AND xylene
OR
Helps to broaden the coverage of a search and increase the number of your results
The OR operator is placed between search terms that have a similar meaning or definition. Using OR tells the database that either term must be present in every hit within your search results. Linking more search terms with the OR operator will increase coverage of your search and the number of results by making the search broader in each instance
Example: If you want to find a wide range of references about polythene, type polythene OR polyethylene OR thermoplastic polymers
NOT
Helps to narrow and focus a Search
The NOT operator eliminates an unwanted search term or group of search terms from the search results.
Example: If you want to find references about cognition, but not those containing information about the environment, type cognition NOT environment