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
hieu quang » thieu quang, hieu quan, hieu qua
chieu sang » chieu sach, chieu xanh, hieu lang
cong dan » cong san, cong tan, cong dong
toan cau » toan cao, toan ban, toan tap

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 quang) or (chieu sang)) - thanh trong quang trung ((cong dan) OR (huong dan)) toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu quang) OR (chieu sang)) - thanh trong quang trung ((cong dan) OR (huong dan)) toan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hieu quang) or (chieu sang)) - thanh trong quang trung ((cong dan) OR (huong dan)) toan cau".
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu quang) or (chieu sang)) - thanh trong quang trung ((cong dan) OR (huong dan)) toan cau*.