Perhaps you should try some spelling variations:
ref history » reef history, bief history, etf history
21 germany » 11 germany, 2 germany, 20 germany
2f history » etf history, tnf history, 7 history
90 20th » 20 20th, 1990 20th
94 20th » 4 20th, 94 24th, 1994 20th

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 %21 germany %((((2f history) OR (((ref history) OR (brief history))))) OR (imf history)) %((90 20th) OR (94 20th)) century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %21 germany %((((2f history) or (((ref history) OR (brief history))))) or (imf history)) %((90 20th) or (94 20th)) century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %21 germany %((((2f history) or (((ref history) OR (brief history))))) or (imf history)) %((90 20th) or (94 20th)) century%22*.