Perhaps you should try some spelling variations:
teaching based » teaching case, teaching cases
teaching aid » teaching aids, teaching a, teaching case
coping shu » cong shu
du credit » de credit, 2 credit
dong nan » dong yang, dong sin, dong bin
a credit » bad credit
nan a » nan ya, can a, jan a

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 nan a ((du credit) OR (a credit)) ((teaching based) OR (teaching aid)) coping shu ;~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "dong nan a ((du credit) or (a credit)) ((teaching based) OR (teaching aid)) coping shu ;~".
• Adding a wildcard symbol may retrieve word variants: dong nan a ((du credit) or (a credit)) ((teaching based) OR (teaching aid)) coping shu ;*.