Perhaps you should try some spelling variations:
thong cong » trong cong, tong cong, thong thong
cong tham » chong tham, cong thai, hong tham
hang cong » dang cong, hang nong, bang cong
doc hieu » toc thieu, hoc thieu, hoc hien
hieu luc » hieu luat, hieu qua
van hang » van khang, van hoang, van thang
hang dau » hang va, hang tai

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc hieu luc - thanh cong tham ((thong cong) or (hang cong)) van hang dau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu luc - thanh cong tham ((thong cong) OR (hang cong)) van hang dau.
• Adding a wildcard symbol may retrieve word variants: doc hieu luc - thanh cong tham ((thong cong) or (hang cong)) van hang dau*.