Perhaps you should try some spelling variations:
thanh tung » thanh cong
thanh dung » thanh duong, thanh hung, hanh dung
hieu sang » chieu sang, hieu lang, hieu quang
doc hieu » toc thieu, hoc thieu, hoc hien
cong dan » cong tan, huong dan, cong dong
cong san » cong tac
toan cau » toan cao, toan ban, toan tap

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

• If you are trying to use Boolean operators, they must be ALL CAPS: doc hieu sang - ((thanh trung) OR (thanh tung)) thanh dung ((cong dan) OR (cong san)) toan cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu sang - ((thanh trung) OR (thanh tung)) thanh dung ((cong dan) or (cong san)) toan cau~".
• Adding a wildcard symbol may retrieve word variants: doc hieu sang - ((thanh trung) OR (thanh tung)) thanh dung ((cong dan) or (cong san)) toan cau*.