Perhaps you should try some spelling variations:
20th century » 18th century
etf history » reef history, ref history, beruf history
tnf history » ref history, motif history, stone history
2f history » ref history, 7 history, reef history
21 germany » 11 germany, 2 germany, 20 germany
25 germany » 5 germany, 2 germany, 20 germany
2f germany » 2 germany, 20 germany, 26 germany
2 german » 3 german, 5 german
2f 20th » 20 20th, 2.2 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 (25 germany))) OR (2 german))) OR (21 germany)) %((((((2f history) OR (tnf history))) OR (etf history))) OR (((imf history) OR (brief history)))) %2f 20th century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %((((((2f germany) OR (25 germany))) or (2 german))) or (21 germany)) %((((((2f history) or (tnf history))) or (etf history))) or (((imf history) or (brief history)))) %2f 20th century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %((((((2f germany) OR (25 germany))) or (2 german))) or (21 germany)) %((((((2f history) or (tnf history))) or (etf history))) or (((imf history) or (brief history)))) %2f 20th century%22*.