Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
toc hieu » toc thieu, doc hieu, hoc thieu
cong tac » cong ty
tac phan » tac pham, tai phan, tac phat
phan dau » phan tu, hang dau
va dang » van dang, va lang, da dang
va nang » van nang, da nang, cam nang

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc hieu quang - canh tranh ((va dang) or (va nang)) cong tac phan dau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc hieu quang - canh tranh ((va dang) OR (va nang)) cong tac phan dau.
• Adding a wildcard symbol may retrieve word variants: toc hieu quang - canh tranh ((va dang) or (va nang)) cong tac phan dau*.