LibAnswers

"Boolean searches allow you to combine words and phrases using the words AND, OR, NOT and NEAR (otherwise known as Boolean operators) to limit, widen, or define your search. Most Internet search engines and Web directories default to these Boolean search parameters anyway, but a good Web searcher should know how to use basic Boolean operators". See more details on Boolean searching.

Here is an example of a search using Boolean operators:

(note that the * after words is a truncation operator - i.e. the search engine will also retrieve plurals/variations. Note also that when you put OR between search terms you must enclose the terms in brackets)

(wetland* OR  marsh* OR swamp*) AND Africa*

AND

(status OR health OR condition* OR stress* OR threat* OR degrad* OR deteriorat*)

AND

(ecolog* OR ecosyst* OR habitat*)

AND

(appraisal* OR impact* OR effect* OR affect* OR assess* OR evaluat*)