Perhaps you should try some spelling variations:
canh trinh » canh tranh, hanh trinh, canh tinh
chat quang » pham quang
cong thanh » dong thanh, cong trinh, cong tan
hieu sang » chieu sang, hieu quang, nhieu tang
hieu lang » chieu sang, hieu quang, nhieu tang
thanh van » thanh san, thanh toan, thanh phan

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 trinh ((chat quang) or (chat luong)) cong thanh van ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sang) OR (hieu lang)) - canh trinh ((chat quang) OR (chat luong)) cong thanh van ban.
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sang) or (hieu lang)) - canh trinh ((chat quang) or (chat luong)) cong thanh van ban*.