Perhaps you should try some spelling variations:
chat quang » chat luong, pham quang
cong thanh » dong thanh, cong trinh, truong thanh
hieu sang » chieu sang, hieu quang, nhieu tang
hieu lang » chieu sang, hieu quang, nhieu tang
canh tinh » hanh tinh, manh tinh, canh tranh
cong tan » cong tac, cong san, cong ty

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc ((hieu sang) or (hieu lang)) - canh tinh chat quang ((cong thanh) or (cong tan)) van ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sang) OR (hieu lang)) - canh tinh chat quang ((cong thanh) OR (cong tan)) van ban.
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sang) or (hieu lang)) - canh tinh chat quang ((cong thanh) or (cong tan)) van ban*.