Perhaps you should try some spelling variations:
chi xanh » chi anh, chi danh, chieu xanh
chi hanh » chi nhanh, chi thanh, thi hanh
cua dung » cua dang, qua dung, cua rung
cua dong » chua dong, cua cong, cua dang
cong bai » cuong bai, cong hai, cung bai
bai toan » bai tap
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: doi ((chi xanh) OR (chi hanh)) - canh tranh ((cua dung) or (cua dong)) cong bai toan cao~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doi ((chi xanh) OR (chi hanh)) - canh tranh ((cua dung) OR (cua dong)) cong bai toan cao.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doi ((chi xanh) OR (chi hanh)) - canh tranh ((cua dung) or (cua dong)) cong bai toan cao".
• Adding a wildcard symbol may retrieve word variants: doi ((chi xanh) OR (chi hanh)) - canh tranh ((cua dung) or (cua dong)) cong bai toan cao*.