Perhaps you should try some spelling variations:
ref history » reef history, brief history, bief history
20 germany » 2 germany, 7 germany, 5 germany
14 germany » 4 germany, 11 germany, 12 germany
8 germany » 7 germany, 1918 germany
20 18th » 2017 18th, 2021 18th, 2018 18th

Try widening your search to All Fields.

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: %22agriculture AND state %((20 germany) OR (((14 germany) OR (8 germany)))) %ref history %20 18th century%22.
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %((20 germany) or (((14 germany) or (8 germany)))) %ref history %20 18th century%22*.