Perhaps you should try some spelling variations:
thieu quang » hieu quang, thien quan, trien quang
thanh trung » thanh tung
thieu sang » chieu sang, thieu khang, hieu lang
trung cua » truong cua, trung tuan, trung cap
dung cong » dung trong
tac toan » tap toan, tam toan, hach toan
toan cao » toan ban, toan tap

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

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