Perhaps you should try some spelling variations:
hieu manh » chieu xanh, hieu nganh, dieu hanh
hanh tran » hanh trang, thanh tran, hanh tram
tac thanh » bac thanh, cac thanh, tcc thanh
doc hieu » toc thieu, hoc thieu, hoc hien
va duong » van duong, va tuong, va huong
tac than » tam than, tac nhan, bac thanh
va dung » van dung, vat dung, va ung

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 manh - hanh tran ((va dung) OR (va duong)) cong ((tac than) OR (tac thanh)) cao~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc hieu manh - hanh tran ((va dung) OR (va duong)) cong ((tac than) or (tac thanh)) cao~".
• Adding a wildcard symbol may retrieve word variants: doc hieu manh - hanh tran ((va dung) OR (va duong)) cong ((tac than) or (tac thanh)) cao*.