Perhaps you should try some spelling variations:
christian upon » christians upon, christianity upon, christ upon
ref history » reef history, brief history, bief history
5th century » 15th century, 6th century, 20th century
21 germany » 11 germany, 2 germany, 20 germany

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: %((christian upon) OR (christian union)) conversations %21 germany %ref history %2020 ((5th century) OR (18th century))%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%((christian upon) or (christian union)) conversations %21 germany %ref history %2020 ((5th century) OR (18th century))%22".
• Adding a wildcard symbol may retrieve word variants: %((christian upon) or (christian union)) conversations %21 germany %ref history %2020 ((5th century) OR (18th century))%22*.