Perhaps you should try some spelling variations:
20th century » 18th century
ref history » reef history, brief history, bief history
26 germany » 25 germany, 27 germany, 28 germany
20 germany » 7 germany, 8 germany, 5 germany
21 germany » 11 germany, 7 germany, 8 germany
6 germany » 7 germany, 8 germany, 5 germany
2 germany » 7 germany, 2 german, 8 germany
2f 20th » 20 20th, 2.2 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 %((((((((26 germany) OR (6 germany))) OR (20 germany))) OR (2 germany))) OR (21 germany)) %ref history %2f 20th century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %((((((((26 germany) OR (6 germany))) or (20 germany))) or (2 germany))) or (21 germany)) %ref history %2f 20th century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %((((((((26 germany) OR (6 germany))) or (20 germany))) or (2 germany))) or (21 germany)) %ref history %2f 20th century%22*.