Perhaps you should try some spelling variations:
hieu nganh » vien nganh, hiem ngan, nghiep nganh
hieu manh » chieu xanh, dieu hanh, hien hanh
hanh tinh » hanh trinh, nhanh tinh, thanh tinh
cong dan » cong tan, huong dan, cong dong
cong san » cong tac
toan tap » toan ban
tinh he » trinh he, hinh he, tinh ha

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

• Performing a fuzzy search may retrieve terms with similar spellings: doc ((hieu nganh) OR (hieu manh)) - hanh tinh he thong ((cong dan) or (cong san)) toan tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu nganh) OR (hieu manh)) - hanh tinh he thong ((cong dan) OR (cong san)) toan tap.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu nganh) OR (hieu manh)) - hanh tinh he thong ((cong dan) or (cong san)) toan tap".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu nganh) OR (hieu manh)) - hanh tinh he thong ((cong dan) or (cong san)) toan tap*.