Perhaps you should try some spelling variations:
20th century » 18th century
2.1 germany » 21 germany, 2017 germany, 9.13 germany
ref history » reef history, bief history, etf history
2f history » 2.1 history, etf history, tnf history
2f 20th » 20 20th, 2.2 20th

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 %2.1 germany %((((((2f history) OR (ref history))) OR (brief history))) OR (imf history)) %2f 20th century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %2.1 germany %((((((2f history) OR (ref history))) or (brief history))) or (imf history)) %2f 20th century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %2.1 germany %((((((2f history) OR (ref history))) or (brief history))) or (imf history)) %2f 20th century%22*.