Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
hanh huong » thanh huong, anh huong, manh huong
nhung cong » dung cong, thong cong, nhung don
hieu lang » chieu sang, nhieu tang, hieu van
huong cua » dung cua
hang cong » dang cong, hang nong, bang cong
dan toan » van toan, dan than, manh toan
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: doi ((hieu lang) OR (hieu quang)) - hanh huong cua ((nhung cong) OR (hang cong)) dan toan cao~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doi ((hieu lang) OR (hieu quang)) - hanh huong cua ((nhung cong) or (hang cong)) dan toan cao~".
• Adding a wildcard symbol may retrieve word variants: doi ((hieu lang) OR (hieu quang)) - hanh huong cua ((nhung cong) or (hang cong)) dan toan cao*.