Perhaps you should try some spelling variations:
20th century » 18th century
ref history » reef history, brief history, bief history
imf history » brief history
2 germany » _ germany, 7 germany, 8 germany
2019 20th » 2019 4th, 2019 6th, 2019 5th
2 german » _ german, 3 german, 5 german

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 %((2 germany) OR (2 german)) %((ref history) OR (imf history)) %2019 20th century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %((2 germany) OR (2 german)) %((ref history) or (imf history)) %2019 20th century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %((2 germany) OR (2 german)) %((ref history) or (imf history)) %2019 20th century%22*.