Perhaps you should try some spelling variations:
chieu sach » chinh sach, chiet tach, chieu sang
hieu quang » thieu quang, hieu quan, hieu qua
thanh tung » thanh cong
van dung » van dong, xay dung, tin dung
cong tap » cuong tap, cong tac, cong tan
tap toan » tap doan, tap quan, bai toan
toan cao » toan ban, toan tap
va dung » va duong, vat dung, va ung

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: ho ((chieu sach) OR (hieu quang)) - thanh tung ((va dung) OR (van dung)) cong tap toan cao~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho ((chieu sach) or (hieu quang)) - thanh tung ((va dung) OR (van dung)) cong tap toan cao~".
• Adding a wildcard symbol may retrieve word variants: ho ((chieu sach) or (hieu quang)) - thanh tung ((va dung) OR (van dung)) cong tap toan cao*.