Perhaps you should try some spelling variations:
bief history » brief history, brief hystory, imf history
20th century » 18th century
ref history » reef history, brief history, imf history
2020 20th » 2020 16th, 2020 2021, 2020 5th

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 %7 germany %((ref history) OR (bief history)) %2020 20th century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %7 germany %((ref history) OR (bief history)) %2020 20th century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %7 germany %((ref history) OR (bief history)) %2020 20th century%22*.