Perhaps you should try some spelling variations:
ref history » reef history, brief history, bief history
21 germany » 11 germany, 20 germany, 7 germany
2 germany » 7 germany, 2 german, 8 germany
2023 20th » 2023 26th, 2020 20th, 2023 24th
2023 10th » 2022 10th, 2023 11th, 2013 10th
90 20th » 20 20th, 1990 20th
94 20th » 4 20th, 1994 20th
94 24th » 94 4th, 94 14th, 24 24th

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 %((21 germany) OR (2 germany)) %ref history %((((2023 20th) OR (2023 10th))) OR (((90 20th) OR (((94 20th) OR (94 24th)))))) century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %((21 germany) or (2 germany)) %ref history %((((2023 20th) OR (2023 10th))) or (((90 20th) or (((94 20th) or (94 24th)))))) century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %((21 germany) or (2 germany)) %ref history %((((2023 20th) OR (2023 10th))) or (((90 20th) or (((94 20th) or (94 24th)))))) century%22*.