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
_ germany » _ german

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) OR (((_ germany) OR (7 germany)))) %((2f history) OR (ref history)) %2.2 ((20th century) OR (18th century))%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %((2f germany) or (((_ germany) or (7 germany)))) %((2f history) OR (ref history)) %2.2 ((20th century) or (18th century))%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %((2f germany) or (((_ germany) or (7 germany)))) %((2f history) OR (ref history)) %2.2 ((20th century) or (18th century))%22*.