Perhaps you should try some spelling variations:
theo hieu » theo chieu, theo tieu, thien hieu
hieu lang » chieu sang, hieu quang, nhieu tang
thang va » hang va, trang va, thong va
cong tap » cuong tap, cong tan, tong tap
cong tac » cong ty
toan cao » toan ban, toan tap
tang va » trang va, tang van, tang vat

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