Perhaps you should try some spelling variations:
20th century » 18th century
ref history » reef history, bief history, etf history
21 germany » 2.1 germany, 20 germany, 1 germany
12 germany » 12 german, 14 germany, 7 germany
11 germany » 11 german, 1918 germany, 7 germany
2 germany » 7 germany, 2 german, 8 germany
20 20th » 90 20th, 2019 20th, 2020 20th

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 %((21 germany) OR (((2 germany) OR (((12 germany) OR (11 germany)))))) %((imf history) OR (((ref history) OR (brief history)))) %20 20th century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %((21 germany) or (((2 germany) or (((12 germany) or (11 germany)))))) %((imf history) or (((ref history) OR (brief history)))) %20 20th century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %((21 germany) or (((2 germany) or (((12 germany) or (11 germany)))))) %((imf history) or (((ref history) OR (brief history)))) %20 20th century%22*.