Use RESET to empty the form.
If you do not know what to enter as a search term, press the "List" button. This will give you a list of keywords where you can select relevant terms.
When entering more then one search terms in a field, separate each term with a semicolon (;).
The semicolon is interpreted by the system according to the choice  of boolean operator.
You may also use the ISIS logical operators:
 + for OR
 * for AND
 ^ for AND NOT
If the field contains ISIS boolean operators the boolean selection does not change them.
If the box "Exact match of words" is marked, you can also use the $ mask for root searching.