Perhaps you should try some spelling variations:
thanh trung » thanh tung
trung thanh » truong thanh
thieu sang » chieu sang, thieu khang, thieu quang
dien quang » diep quang, trien quang, lien quan
thanh dung » thanh duong, thanh tung, thanh hung
dung cong » dung trong
tap toan » tap doan, tap quan
bai toan » bai 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 ((thieu sang) or (dien quang)) - thanh trung thanh dung cong ((tap toan) or (bai toan)) cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((thieu sang) OR (dien quang)) - thanh trung thanh dung cong ((tap toan) OR (bai toan)) cau.
• Adding a wildcard symbol may retrieve word variants: hoc ((thieu sang) or (dien quang)) - thanh trung thanh dung cong ((tap toan) or (bai toan)) cau*.