Perhaps you should try some spelling variations:
tieu xanh » tieu danh, chieu xanh, dieu hanh
hanh tang » hanh trang, anh tang, hanh tung
hanh mang » nhanh mang, hanh trang, nhanh lang
dung cong » dung trong
van toan » van tuan, van tan, van thanh
tap toan » tap doan, tap quan, bai toan
va dung » van dung, va duong, vat dung

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 - ((hanh tang) OR (hanh mang)) va dung cong ((van toan) OR (tap toan)) cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "theo tieu xanh - ((hanh tang) OR (hanh mang)) va dung cong ((van toan) or (tap toan)) cau~".
• Adding a wildcard symbol may retrieve word variants: theo tieu xanh - ((hanh tang) OR (hanh mang)) va dung cong ((van toan) or (tap toan)) cau*.