Perhaps you should try some spelling variations:
nhung cong » dung cong, thong cong, hang cong
thanh tung » thanh cong
hang nong » thang long, han tong
doc hieu » toc thieu, hoc thieu, hoc hien
hieu luc » hieu luat, hieu qua
tung cua » trung cua, tuong cua, dung cua
dan toan » van toan, dan than, manh toan
toan cau » toan cao, toan ban, toan tap

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 tung cua ((nhung cong) or (hang nong)) dan toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu luc - thanh tung cua ((nhung cong) OR (hang nong)) dan toan cau.
• Adding a wildcard symbol may retrieve word variants: doc hieu luc - thanh tung cua ((nhung cong) or (hang nong)) dan toan cau*.