Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
hieu lang » chieu sang, nhieu tang, hieu van
bang cong » dang cong, bang song, hang cong
tich toan » tinh toan, tich than, trinh toan
anh dang » anh dong, anh dung, anh bang
tam toan » tap toan, tam than, pham toan
dang va » dang van, dang vat, hang va
va bang » va nang, va lang, va ban

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 ((hieu lang) OR (hieu quang)) - anh dang va bang cong ((tich toan) OR (tam toan)) cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho ((hieu lang) OR (hieu quang)) - anh dang va bang cong ((tich toan) or (tam toan)) cau~".
• Adding a wildcard symbol may retrieve word variants: ho ((hieu lang) OR (hieu quang)) - anh dang va bang cong ((tich toan) or (tam toan)) cau*.