Perhaps you should try some spelling variations:
thanh duong » thanh huong, thanh cuong, thanh vuong
thanh dung » thanh tung, thanh hung, hanh dung
thong cong » trong cong, tong cong, thong thong
hieu lang » chieu sang, hieu quang, nhieu tang
cua thong » cua thuong, cua khong, cua tong
doc hieu » toc thieu, hoc thieu, hoc hien
dan than » dan chan, ban than, van than

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 lang - ((thanh dung) OR (thanh duong)) cua thong cong ((dan than) or (dan gian)) cap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu lang - ((thanh dung) OR (thanh duong)) cua thong cong ((dan than) OR (dan gian)) cap.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu lang - ((thanh dung) OR (thanh duong)) cua thong cong ((dan than) or (dan gian)) cap".
• Adding a wildcard symbol may retrieve word variants: doc hieu lang - ((thanh dung) OR (thanh duong)) cua thong cong ((dan than) or (dan gian)) cap*.