Perhaps you should try some spelling variations:
luan nhung » luan chung, luan hung, quan nhung
nhung cong » dung cong, thong cong, hang cong
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
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 nhung cong ((tan tran) OR (tap toan)) cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doc ((hieu xanh) OR (hieu manh)) - hanh tang luan nhung cong ((tan tran) or (tap toan)) cau~".
• Adding a wildcard symbol may retrieve word variants: doc ((hieu xanh) OR (hieu manh)) - hanh tang luan nhung cong ((tan tran) or (tap toan)) cau*.