Perhaps you should try some spelling variations:
chieu xanh » chieu sach, chieu sang, chieu tinh
hanh trang » thanh trung, canh tranh, hanh trinh
nhung cong » dung cong, thong cong, hang cong
tieu xanh » tieu danh, dieu hanh, tien anh
trang va » tran van, hang va
tap toan » tap quan, bai toan
tap doan » tap quan

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

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