Once you have a list of results, you can use the limits options available in the Refine Results bar to the left of the screen to add additional terms to your search or to restrict your search by subject area, document type, publication date, language, etc.
Click on the arrow next to the limit of your choice.
The most frequently occurring limits only are displayed. To view all options, click on the see all link.
Select the limits of your choice by checking the appropriate boxes.
Then click on the Refine or Exclude buttons. The exclude button is available if you click the see all link at the bottom of each category.