Perhaps you should try some spelling variations:
credit training » credit rationing, credit rating, credit granting
credit trading » credit rating, credit standing, credit creating
courses taking » course taking, courses changing, courses enabling
taking hui » taking up, taking due, taking our
yang yang » wang yang, wang yan
yang yaa » yang yao, yang maha, yang yera

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: dong ((yang yaa) OR (yang yang)) du ((credit training) OR (credit trading)) courses taking hui ;~.
• Adding a wildcard symbol may retrieve word variants: dong ((yang yaa) or (yang yang)) du ((credit training) or (credit trading)) courses taking hui ;*.