Perhaps you should try some spelling variations:
hieu manh » chieu xanh, hieu nganh, dieu hanh
tranh qua » tranh cua, thanh qua, trinh qua
dung cong » dung trong
hoc hieu » hoc thieu, hoc hien, doc hieu
qua dung » quang dung, su dung, qua song
van toan » van tuan, van tan, van thanh
bai toan » bai tap

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 manh - canh tranh qua dung cong ((van toan) or (bai toan)) ban~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc hieu manh - canh tranh qua dung cong ((van toan) OR (bai toan)) ban.
• Adding a wildcard symbol may retrieve word variants: hoc hieu manh - canh tranh qua dung cong ((van toan) or (bai toan)) ban*.