Perhaps you should try some spelling variations:
ref history » reef history, brief history, bief history
2f germany » 2 germany, 20 germany, 21 germany
2f history » imf history, etf history, tnf history
1990 20th » 1995 20th, 1999 20th, 1990 2000
1994 20th » 1995 20th, 1999 20th, 1994 24th
1994 10th » 1994 15th, 1994 19th, 1995 10th
90 20th » 20 20th, 94 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 (1990 20th))) OR (((1994 20th) OR (1994 10th)))) 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 (1990 20th))) or (((1994 20th) OR (1994 10th)))) century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %2f germany %((2f history) or (ref history)) %((((90 20th) or (1990 20th))) or (((1994 20th) OR (1994 10th)))) century%22*.