Perhaps you should try some spelling variations:
christian oboen » christian about, christian onof, christian order
christian boehm » christian both, christian behl, christian beck
reef history » brief history, reeves history, reef fishery
20th century » 18th century
ref history » brief history, bief history, imf history
2 germany » 7 germany, 2 german, 8 germany
20 20th » 90 20th, 2019 20th, 2020 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: %((christian oboen) OR (christian boehm)) conversations %2 germany %((reef history) OR (ref history)) %20 20th century%22.
• Adding a wildcard symbol may retrieve word variants: %((christian oboen) or (christian boehm)) conversations %2 germany %((reef history) or (ref history)) %20 20th century%22*.