Perhaps you should try some spelling variations:
theo hieu » theo chieu, theo tieu, thien hieu
hieu lang » chieu sang, hieu quang, nhieu tang
cong tan » cong san, cong thanh, cong ty
cong tac » cong ty
toan tap » toan ban
vi dung » va dung, vi dong, viet dung
vi ung » va ung, vi luong, vi trung

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 ((vi dung) or (vi ung)) ((cong tan) OR (cong tac)) toan tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: theo hieu lang - canh tranh ((vi dung) OR (vi ung)) ((cong tan) OR (cong tac)) toan tap.
• The words AND, OR and NOT may confuse the search; try adding quotes: "theo hieu lang - canh tranh ((vi dung) or (vi ung)) ((cong tan) OR (cong tac)) toan tap".
• Adding a wildcard symbol may retrieve word variants: theo hieu lang - canh tranh ((vi dung) or (vi ung)) ((cong tan) OR (cong tac)) toan tap*.