Perhaps you should try some spelling variations:
theo hieu » theo chieu, theo tieu, thien hieu
hieu lang » chieu sang, hieu quang, nhieu tang
tranh cua » doanh cua, manh cua
tong cong » trong cong, cong cong, dung cong
cua tong » cua cong, cua dong, cua nong
dan toan » van toan, dan than, manh toan
bai toan » bai tap

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

• Performing a fuzzy search may retrieve terms with similar spellings: theo hieu lang - canh tranh cua tong cong ((dan toan) or (bai toan)) ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: theo hieu lang - canh tranh cua tong cong ((dan toan) OR (bai toan)) ban*.