Clicking the Previous Searches button on the toolbar (found in the banner area at the top of the page) displays a history of the searches you've conducted during your current session. The most recent search, known as a result set, is at the top of the list with a maximum of 50 result sets displayed.
To re-execute a search from the list, click the hyperlinked search expression. To modify a search, click the Revise link. You will be taken the appropriate search input page and your search terms will be automatically re-displayed. You can then change the search as needed.
The list of previous searches is automatically cleared when you exit out of the session. You may also clear the list by clicking the Clear button.