Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu qua, diep quang
hieu quan » hieu qua, lieu quan, thien quan
bang cong » dang cong, bang song, hang cong
hach toan » thanh toan, manh toan
pham toan » pham tuan, pham tan, phap toan
anh dang » anh dong, anh dung, anh bang
dang van » hoang van, hang va
van bang » van ban, van nang, von bang

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