Boolean logic is used to combine key elements of your search statement in a variety of ways.
The Boolean commands or "operators" AND, OR, and NOT are
used to narrow, expand, and exclude items in a search statement.
Use an AND statement with a very specific
topic. Use of the AND operator will reduce the number of
items returned. e.g. Population AND Control will return
only items containing both "Population" and
Use an OR statement when the topic might be described in a number of different
ways. Use of the OR operator will enlarge the number of items
returned. e.g. Population OR Populated will return all
items containing either "Population" or
Use a NOT statement when the topic is related
to a non-desired topic. Use of the NOT operator will
eliminate items containing the term following the operator. e.g.
Population NOT Student will return all items containing
"Population" except for those items containing
Use truncation when the system permits it, as in forest* (for forest, forests,