Perhaps you should try some spelling variations:
hieu nganh » vien nganh, hiem ngan, hieu manh
vien thanh » viet thanh, tien thanh, dien thanh
nhung cong » dung cong, thong cong, hang cong
tranh va » tranh van, trang va, trinh va
san toan » dan toan, manh toan, xuan toan
van toan » van tuan, van tan, van thanh

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc ((hieu nganh) or (vien thanh)) - canh tranh va nhung cong ((san toan) OR (van toan)) cao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc ((hieu nganh) OR (vien thanh)) - canh tranh va nhung cong ((san toan) OR (van toan)) cao.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hieu nganh) or (vien thanh)) - canh tranh va nhung cong ((san toan) OR (van toan)) cao".
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu nganh) or (vien thanh)) - canh tranh va nhung cong ((san toan) OR (van toan)) cao*.