Perhaps you should try some spelling variations:
2.1 germany » 2017 germany, 9.13 germany, 9.14 germany
ref history » reef history, brief history, bief history
21 germany » 11 germany, 2 germany, 20 germany
90 20th » 20 20th, 1990 20th
94 20th » 4 20th, 94 24th, 1994 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) OR (21 germany)) %ref history %((90 20th) OR (94 20th)) century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %((2.1 germany) OR (21 germany)) %ref history %((90 20th) or (94 20th)) century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %((2.1 germany) OR (21 germany)) %ref history %((90 20th) or (94 20th)) century%22*.