Perhaps you should try some spelling variations:
hieu nganh » vien nganh, hiem ngan, hieu manh
nhung cong » thong cong, hang cong, nhung don
hieu xanh » chieu xanh, hieu manh, dieu hanh
dong luan » dung luan, tong luan, dong xuan
dung cong » dung trong
dan than » dan chan, ban than, van than
than cao » toan cao, thai cao, than cap
ha dong » hoat dong, van dong

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 xanh) OR (hieu nganh)) - ha dong luan ((nhung cong) OR (dung cong)) dan than cao~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu xanh) OR (hieu nganh)) - ha dong luan ((nhung cong) or (dung cong)) dan than cao~".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu xanh) OR (hieu nganh)) - ha dong luan ((nhung cong) or (dung cong)) dan than cao*.