Perhaps you should try some spelling variations:
thieu sang » chieu sang, thieu khang, thieu quang
hanh trang » thanh trung, hanh trinh, minh trang
hoc thieu » toc thieu, hoc hien
dung cong » dung trong
hach toan » thanh toan, manh toan
tac toan » tap toan, tam toan, tich toan
va dung » van dung, va duong, vat dung

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: hoc thieu sang - ((hanh trang) OR (canh tranh)) va dung cong ((tac toan) OR (hach toan)) cao~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc thieu sang - ((hanh trang) OR (canh tranh)) va dung cong ((tac toan) or (hach toan)) cao~".
• Adding a wildcard symbol may retrieve word variants: hoc thieu sang - ((hanh trang) OR (canh tranh)) va dung cong ((tac toan) or (hach toan)) cao*.