Perhaps you should try some spelling variations:
hieu nganh » vien nganh, hiem ngan, hieu manh
hieu lang » chieu sang, hieu quang, nhieu tang
hanh mang » nhanh mang, hanh trang, nhanh lang
cong tan » cong tac, cong thanh, cong ty
cong san » cong tac
toan cau » toan cao, toan ban, toan tap
mang va » mang vua, hang va, bang va

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