Perhaps you should try some spelling variations:
thanh trong » thanh trung, tranh trong, hanh trong
trong quang » truong quang, thong quang, trong quan
quang trung » truong trung
chieu sang » chieu sach, chieu xanh, hieu lang
trung cong » truong cong, trong cong, trung uong
hieu quan » hieu qua, lieu quan, thien quan
cong dan » cong san, cong tan, huong dan
dan toan » van toan, dan than, manh toan
toan ban » van ban

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((hieu quan) or (chieu sang)) - thanh trong quang trung cong dan toan ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu quan) OR (chieu sang)) - thanh trong quang trung cong dan toan ban.
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu quan) or (chieu sang)) - thanh trong quang trung cong dan toan ban*.