Nesting is a keyword searching technique that utilizes parentheses to clarify relationships between search terms. Using Nesting in your search requires that the items in parentheses be searched first. Generally the items in parentheses are linked by the Boolean Operator "OR."
Use Nesting when you are trying to link two or more concepts that may have many synonyms, or may be represented by a number of different terms to obtain more comprehensive search results.
Select the Advanced Search option from the "Other Searches" box on the right side of the initial search screen. Select the desired search from the dropdown menu, and type in your search terms.
Supose that one searched for (energy OR solar) AND global warming. First, the resource would create the set that is the combination of Energy and Solar (Step 1 and 2 below). Then it would that that combined set and find its intersection with Global Warming (step 3 below). The result would be the pale green area, the intersection.