Perhaps you should try some spelling variations:
ref history » reef history, bief history, etf history
21 germany » 11 germany, 2 germany, 20 germany
2018 10th » 2015 10th, 2013 10th, 2018 4th
2018 14th » 2018 4th, 2018 5th

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 %21 germany %((ref history) OR (((imf history) OR (brief history)))) %((((2018 10th) OR (2018 14th))) OR (2018 15th)) century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%22agriculture and state %21 germany %((ref history) or (((imf history) OR (brief history)))) %((((2018 10th) or (2018 14th))) or (2018 15th)) century%22".
• Adding a wildcard symbol may retrieve word variants: %22agriculture and state %21 germany %((ref history) or (((imf history) OR (brief history)))) %((((2018 10th) or (2018 14th))) or (2018 15th)) century%22*.