The tree on the right contains the subjects and titles available for retrieval. You can select one or more subjects or titles by clicking on the box in front of its name. If you select a subject, all the titles under the subject are selected. If you unselect a subject, all the titles under the subject are unselected.
If there is a plus sign in front of the subject box, you can click on it see and select the titles under that subject. Click on the minus sign if you close up the title list.