Perhaps you should try some spelling variations:
trading volumes » trading volume, trade volumes
credit trading » credit training, credit rating, credit standing
volumes cong » volume one, volumes book
dual credit » rural credit, deals credit, equal credit
yang yang » wang yan
wang yang » wang yan, wang liang, wang yanling
done sin » dong sin, done using, done so
a dual » _ dual

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: ((done sin) OR (((yang yang) OR (wang yang)))) a dual credit trading volumes cong shu ;~.
• Adding a wildcard symbol may retrieve word variants: ((done sin) or (((yang yang) or (wang yang)))) a dual credit trading volumes cong shu ;*.