Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
hanh trang » thanh trung, canh tranh, hanh trinh
hieu lang » chieu sang, nhieu tang, hieu van
hanh tang » anh tang, hanh mang, hanh tung
dung cong » dung trong
cong san » cong tac
san toan » van toan, dan toan, manh toan
toan cau » toan cao, toan ban, toan tap
va dung » van dung, va duong, vat dung

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) OR (hanh trang)) va dung 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) OR (hanh trang)) va dung cong san toan cau~".
• Adding a wildcard symbol may retrieve word variants: ho ((hieu lang) or (hieu quang)) - ((hanh tang) OR (hanh trang)) va dung cong san toan cau*.