When a user selects a single heading (Subject, Journal, Author, etc.) from a facet on the result list and clicks Update, the heading is added to the search terms with the AND operator, limiting results to only those related to the search terms and subject heading.
- (search term AND heading)
(heart disease AND TREATMENT)
When multiple headings are selected from a facet before clicking the Update button, the headings are added to the search terms with the OR operator to prevent the user from receiving zero results.
- (search term AND (heading OR heading OR heading))
(heart disease AND (TREATMENT OR CORONARY heart disease OR CONGENITAL heart disease))
Note: If you would like to limit your search to fewer results by using multiple headings, it is recommended that you select one subject heading and update the search before adding an additional heading.