Perhaps you should try some spelling variations:
1918 germany » 8 germany
ref history » reef history, brief history, bief history
11 germany » 11 german, 7 germany, 8 germany
2020 20th » 2020 16th, 2020 5th, 2020 4th

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 %((11 germany) OR (1918 germany)) %ref history %((2020 20th) OR (2020 2021)) century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %((11 germany) OR (1918 germany)) %ref history %((2020 20th) or (2020 2021)) century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %((11 germany) OR (1918 germany)) %ref history %((2020 20th) or (2020 2021)) century%22*.