Use the Advanced Search form to combine fields.
The Title and Keywords field is a free text box. Just type in your keywords into this field.
The Subject field is a pull-down list with an autocomplete feature. Start to type in a subject and the system will offer up to 10 subjects that start with the characters you started to type. If you are not able to find the subject you need, add a few more characters. Point your curser and click on your selection. (just hitting Enter does not work). You can select more than one subject by adding a coma and selecting another subject.
The Population and Language fields are pull-down lists. Point your curser and click on your selection. You can select more than one term by holding down the CTRL key while selecting.
The Format field is a pull down list. Point your curser and click on your selection. You may select only one option in the Format field.