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

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 %((ref history) OR (reef 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 %((ref history) OR (reef history)) %((2020 20th) or (2020 2021)) century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %11 germany %((ref history) OR (reef history)) %((2020 20th) or (2020 2021)) century%22*.