Perhaps you should try some spelling variations:
theo hieu » theo chieu, theo tieu, thien hieu
hieu lang » chieu sang, hieu quang, nhieu tang
cong tan » cong tac, cong thanh, cong ty
cong san » cong tac
phan dau » phan tu, hang dau
va dung » van dung, va duong, vat dung
doan » doanh, dan, toan

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

• Performing a fuzzy search may retrieve terms with similar spellings: theo hieu lang - chan doan va dung ((cong tan) or (cong san)) phan dau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: theo hieu lang - chan doan va dung ((cong tan) OR (cong san)) phan dau.
• Adding a wildcard symbol may retrieve word variants: theo hieu lang - chan doan va dung ((cong tan) or (cong san)) phan dau*.