Perhaps you should try some spelling variations:
christianity upon » christianity among, christianity along, christianity from
christian unity » christian union, christian laity, christian divinity
20th century » 18th century
reef history » brief history, reeves history, reef fishery
bief history » brief history, brief hystory, imf history
ref history » brief history, imf history, etf history
21 germany » 11 germany, 2 germany, 7 germany
20 germany » 2 germany, 7 germany, 8 germany
2f 20th » 20 20th, 2.2 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: %((christianity upon) OR (christian unity)) conversations %((20 germany) OR (21 germany)) %((((ref history) OR (bief history))) OR (reef history)) %2f 20th century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%((christianity upon) or (christian unity)) conversations %((20 germany) or (21 germany)) %((((ref history) OR (bief history))) or (reef history)) %2f 20th century%22".
• Adding a wildcard symbol may retrieve word variants: %((christianity upon) or (christian unity)) conversations %((20 germany) or (21 germany)) %((((ref history) OR (bief history))) or (reef history)) %2f 20th century%22*.