Nesting

Nesting involves using parentheses to insure that Boolean operations are performed in the sequence you intend. This technique allows you to build a complex search using two or more operators (AND, OR, NOT).

CAUTION! You may not build a good search using more than one Boolean operator without using nesting.

Example of simple nesting:

    Find: smoking AND (adolescents OR teenagers)

In this search the OR operation is nested and will be performed first. Then the AND operation will be performed. This search will retrieve items on smoking and adolescents as well as items on smoking and teenagers.

Example of more complex nesting:

    Find: (smoking OR tobacco OR nicotine) AND (adolescents OR teenagers)

The OR operations inside both sets of parentheses will be performed first, and then the resulting sets will be combined using the AND operator. Nesting synonyms in this way can broaden your search.

BAD Example:

    Find: smoking OR tobacco AND adolescents OR teenagers

This search will perform the OR and AND operations in the sequence that they are typed. This will retrieve items that are irrelevant! You will retrieve all items about teenagers, not just those relating to smoking.

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