NB: Sometimes it is better to search individual terms as separate subject headings so as to cast as wide a net as possible. For example, searching for "science" and "history" as seperate terms in the subject field will pull back results that have the subject heading "Science -- Europe -- History -- 17th century," which would not appear if you're just searching "Science -- History." As a rule of thumb, t's best to try different combinations until you find something that works.
