Perhaps you should try some spelling variations:
thanh trung » thanh tung
hieu quang » thieu quang, hieu quan, hieu qua
nhung cong » dung cong, thong cong, hang cong
hieu sang » chieu sang, hieu lang, nhieu tang
cua nhung » va nhung
cong tap » cuong tap, cong tac, cong tan
tap toan » tap doan, tap quan, bai toan
toan cau » toan cao, toan ban, toan tap

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 sang) OR (hieu quang)) - ((canh tranh) or (thanh trung)) cua nhung cong tap toan cau~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doc ((hieu sang) OR (hieu quang)) - ((canh tranh) OR (thanh trung)) cua nhung cong tap toan cau.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu sang) OR (hieu quang)) - ((canh tranh) or (thanh trung)) cua nhung cong tap toan cau".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu sang) OR (hieu quang)) - ((canh tranh) or (thanh trung)) cua nhung cong tap toan cau*.