Perhaps you should try some spelling variations:
reef history » brief history, reeves history, reef fishery
ref history » brief history, bief history, imf history
20 germany » 2 germany, 7 germany, 8 germany
2f germany » 2 germany, 21 germany, 25 germany
1990 20th » 1995 20th, 1999 20th, 1994 20th
20 20th » 2019 20th, 2020 20th, 2023 20th
90 20th » 94 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 %((2f germany) OR (20 germany)) %((ref history) OR (reef history)) %((20 20th) OR (((90 20th) OR (1990 20th)))) century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %((2f germany) or (20 germany)) %((ref history) or (reef history)) %((20 20th) or (((90 20th) OR (1990 20th)))) century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %((2f germany) or (20 germany)) %((ref history) or (reef history)) %((20 20th) or (((90 20th) OR (1990 20th)))) century%22*.