Perhaps you should try some spelling variations:
ref history » reef history, bief history, imf history
2f germany » 2 germany, 20 germany, 21 germany
90 20th » 20 20th, 1990 20th
94 20th » 94 24th, 1994 20th
4 20th » _ 20th, a 20th, 1 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 %((ref history) OR (brief history)) %((90 20th) OR (((((94 20th) OR (4 20th))) OR (19((94 20th) OR (4 20th)))))) century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %2f germany %((ref history) or (brief history)) %((90 20th) or (((((94 20th) OR (4 20th))) or (19((94 20th) OR (4 20th)))))) century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %2f germany %((ref history) or (brief history)) %((90 20th) or (((((94 20th) OR (4 20th))) or (19((94 20th) OR (4 20th)))))) century%22*.