Perhaps you should try some spelling variations:
hanh trinh » canh tranh, hanh chinh
hanh tranh » canh tranh, hanh trang, lanh tranh
nhung cong » dung cong, thong cong, hang cong
chi xanh » chi anh, chi danh, chi hanh
tap toan » tap doan, bai toan
tap quan » tac quan, hai quan
doi chi » doi khi

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 - ((hanh tranh) or (hanh trinh)) va nhung cong ((tap toan) OR (tap quan)) tap~.
• If you are trying to use Boolean operators, they must be ALL CAPS: doi chi xanh - ((hanh tranh) OR (hanh trinh)) va nhung cong ((tap toan) OR (tap quan)) tap.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doi chi xanh - ((hanh tranh) or (hanh trinh)) va nhung cong ((tap toan) OR (tap quan)) tap".
• Adding a wildcard symbol may retrieve word variants: doi chi xanh - ((hanh tranh) or (hanh trinh)) va nhung cong ((tap toan) OR (tap quan)) tap*.