Perhaps you should try some spelling variations:
thanh trung » thanh tung
trung cua » truong cua, trung tuan, trung cap
cua trong » cua truong, cua trung, qua trong
hieu luc » hieu luat
cong san » cong tac
san tan » van tan, san van, san tay
tan tap » toan tap, han tap, tan tat

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((hieu luc) or (hieu qua)) - thanh trung cua trong cong san tan tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu luc) OR (hieu qua)) - thanh trung cua trong cong san tan tap*.