Perhaps you should try some spelling variations:
thong cong » trong cong, tong cong, thong thong
theo hieu » theo chieu, theo tieu, thien hieu
hieu lang » chieu sang, hieu quang, nhieu tang
tranh cua » manh cua
doanh cua » doanh luan
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) OR (doanh cua)) thong 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) OR (doanh cua)) thong cong ((dan toan) OR (bai toan)) ban*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "theo hieu lang - canh ((tranh cua) OR (doanh cua)) thong cong ((dan toan) or (bai toan)) ban*".