The Combine function uses "Boolean" set theory (AND) or (OR) to merge search topics. By using Combine, the searcher is able to join at least two topics and eliminate duplicates from the retrieved citations.

Combining search topics can only be performed after two or more searches have been completed. There must be at least two search sets in the search history.
Click on to combine search topics.

Using AND:
Both topics are required in the retrieved citations.
Topics are usually not synonymous.
Select topic 1 (Diabetes mellitus) by clicking in the box to the left of the topic.
AND select topic 2 (Delivery of health care) by clicking in the box to the left of the topic.

Click on

Retrieval from combining search statements using AND.

Using OR:
Either or both terms may be in the retrieved citations.
Terms OR topics are usually synonymous OR similar.

Select OR from the combine selections menu.
Click in the boxes to select the similar terms to be combined.
Click on

Retrieval from combining search statements using OR.

Remember: Using AND retrieves citations that must have both topics. By combining using AND, the number of citations retrieved will be some number less than or equal to the topic with the least number of citations.

Using OR retrieves citations that must have either, but may have both terms. By combining using OR, the number of citations retrieved will be some number greater than or equal to the topic with the largest number of citations.

The Combine feature helps create a new search set that represents the intersection (AND) or union (OR) of two or more previously created sets.

-- Kathryn E. Kerdolff
kkerdo@lsuhsc.edulink removed