Perhaps you should try some spelling variations:
20th century » 18th century
tnf history » motif history, stone history, reef history
etf history » reef history, beruf history, ethis history
ref history » reef history, bief history, reform history
2f history » 7 history, reef history, bief history
21 germany » 11 germany, 2 germany, 20 germany
2f germany » 2 germany, 20 germany, 25 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 (2 german))) OR (21 germany)) %((((((((2f history) OR (ref 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 (2 german))) or (21 germany)) %((((((((2f history) OR (ref 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 (2 german))) or (21 germany)) %((((((((2f history) OR (ref history))) or (tnf history))) or (etf history))) or (((imf history) or (brief history)))) %2f 20th century%22*.