Perhaps you should try some spelling variations:
20th century » 18th century
reef history » brief history, reeves history, reef fishery
etf history » ref history, beruf history, ethis history
tnf history » ref history, motif history, stone history
imf history » brief history
21 germany » 11 germany, 20 germany, 7 germany
2f history » ref history, 7 history, bief history
26 germany » 6 germany, 20 germany, 25 germany
2 germany » 7 germany, 2 german, 8 germany
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 %((((26 germany) OR (2 germany))) OR (21 germany)) %((((((2f history) OR (reef history))) OR (((etf history) OR (tnf history))))) OR (imf history)) %2f 20th century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %((((26 germany) or (2 germany))) or (21 germany)) %((((((2f history) OR (reef history))) or (((etf history) or (tnf history))))) or (imf history)) %2f 20th century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %((((26 germany) or (2 germany))) or (21 germany)) %((((((2f history) OR (reef history))) or (((etf history) or (tnf history))))) or (imf history)) %2f 20th century%22*.