Perhaps you should try some spelling variations:
hieu xanh » chieu xanh, hieu nganh, dieu hanh
hieu manh » chieu xanh, hieu nganh, dieu hanh
hanh tang » hanh trang, anh tang, hanh mang
tang luan » dung luan
luan dung » lan dung, luan dong, luan hung
dung cong » dung trong
tap toan » tap doan, tap quan, bai toan

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: doc ((hieu xanh) OR (hieu manh)) - hanh tang luan dung cong ((tan tran) OR (tap toan)) cau~.
• Adding a wildcard symbol may retrieve word variants: doc ((hieu xanh) or (hieu manh)) - hanh tang luan dung cong ((tan tran) or (tap toan)) cau*.