Perhaps you should try some spelling variations:
thanh trung » thanh tung
cong thanh » dong thanh, cong trinh, cong tan
thanh than » thanh thanh, thanh thang, thanh toan
hieu tinh » chieu tinh, lieu tinh, kieu tinh
dung cong » dung trong
doc hieu » toc thieu, hoc thieu, hoc hien
cua dung » cua dang, cua dong, qua dung
than cao » toan cao, thai cao, than cap

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: doc hieu tinh - ((thanh trung) OR (canh tranh)) cua dung cong thanh than cao~.
• Adding a wildcard symbol may retrieve word variants: doc hieu tinh - ((thanh trung) or (canh tranh)) cua dung cong thanh than cao*.