Perhaps you should try some spelling variations:
luan thuong » luat thuong, lan thuong, luan phuong
thanh dung » thanh duong, thanh tung, thanh hung
hieu lang » chieu sang, hieu quang, nhieu tang
trong dan » trong dang, trong san, trong ban
trong tan » trong quan, trong cac, trong ca
doi hieu » doi chieu, doc hieu, doi hien

You may be able to get more results by adjusting your search query.

• The words AND, OR and NOT may confuse the search; try adding quotes: "doi hieu lang - thanh dung luan thuong ((trong dan) OR (trong tan)) van ban~".
• Adding a wildcard symbol may retrieve word variants: doi hieu lang - thanh dung luan thuong ((trong dan) OR (trong tan)) van ban*.