Perhaps you should try some spelling variations:
ref history » reef history, brief history, bief history
2f history » imf history, etf history, tnf history
2f germany » 2 germany, 20 germany, 21 germany
1994 20th » 1995 20th, 1999 20th, 1990 20th
94 20th » 4 20th, 94 24th
90 20th » 20 20th, 1990 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 %((2f history) OR (ref history)) %((((((90 20th) OR (94 20th))) OR (19((90 20th) OR (94 20th))))) OR (1994 20th)) century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %2f germany %((2f history) or (ref history)) %((((((90 20th) OR (94 20th))) or (19((90 20th) OR (94 20th))))) or (1994 20th)) century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %2f germany %((2f history) or (ref history)) %((((((90 20th) OR (94 20th))) or (19((90 20th) OR (94 20th))))) or (1994 20th)) century%22*.