Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
hieu lang » chieu sang, nhieu tang, hieu van
hanh tang » hanh trang, anh tang, hanh mang
va duong » van duong, va tuong, va huong
cong san » cong tac
san toan » van toan, dan toan, manh toan
toan cau » toan cao, toan ban, toan tap
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: ho ((hieu lang) OR (hieu quang)) - hanh tang ((va dung) OR (va duong)) cong san toan cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho ((hieu lang) or (hieu quang)) - hanh tang ((va dung) OR (va duong)) cong san toan cau~".
• Adding a wildcard symbol may retrieve word variants: ho ((hieu lang) or (hieu quang)) - hanh tang ((va dung) OR (va duong)) cong san toan cau*.