Perhaps you should try some spelling variations:
trading case » trading costs, trade case
dual credit » rural credit, deals credit, equal credit
du credit » de credit, 2 credit
case cong » case cost
a credit » bad credit
yan yao » yang yao, gang yao, yan yuan
wang » wing, wan, lang

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: wang yan yao ((((a credit) or (du credit))) or (dual credit)) trading case cong shu ;~.
• If you are trying to use Boolean operators, they must be ALL CAPS: wang yan yao ((((a credit) OR (du credit))) OR (dual credit)) trading case cong shu ;.
• Adding a wildcard symbol may retrieve word variants: wang yan yao ((((a credit) or (du credit))) or (dual credit)) trading case cong shu ;*.