Perhaps you should try some spelling variations:
thanh trung » thanh tung
chieu sang » chieu sach, chieu xanh, hieu lang
trung quan » truong quan, trong quan, trung tuan
quan trung » quang trung, quan trong, xuan trung
hieu sang » hieu lang, hieu quang, nhieu tang
cong tac » cong ty
khoa cam » khoan cam, khoa kham, khoa ma

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 (chieu sang)) - thanh trung quan trung ((cong san) OR (cong tac)) khoa cam~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sang) OR (chieu sang)) - thanh trung quan trung ((cong san) OR (cong tac)) khoa cam.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu sang) or (chieu sang)) - thanh trung quan trung ((cong san) OR (cong tac)) khoa cam".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sang) or (chieu sang)) - thanh trung quan trung ((cong san) OR (cong tac)) khoa cam*.