Perhaps you should try some spelling variations:
human conversations » human conversation, human conversational, roman conversations
open conversations » agent conversations, roman conversations, content conversations
bief history » brief history, brief hystory, reef history
20th century » 18th century
ref history » reef history, brief history, etf history
imf history » brief history
21 germany » 11 germany, 2 germany, 20 germany
2020 20th » 2020 16th, 2020 2021, 2020 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: %christian ((human conversations) OR (open conversations)) %21 germany %((ref history) OR (((bief history) OR (imf history)))) %2020 20th century%22.
• The words AND, OR and NOT may confuse the search; try adding quotes: "%christian ((human conversations) or (open conversations)) %21 germany %((ref history) or (((bief history) OR (imf history)))) %2020 20th century%22".
• Adding a wildcard symbol may retrieve word variants: %christian ((human conversations) or (open conversations)) %21 germany %((ref history) or (((bief history) OR (imf history)))) %2020 20th century%22*.