Perhaps you should try some spelling variations:
thieu xanh » chieu xanh, hieu manh, thien anh
cang thang » cong thanh, dang thanh
hoc thieu » toc thieu, hoc hien
vat dung » van dung, viet dung, mat duong
tap toan » tap quan, bai toan
tap doan » tap quan
va dung » van dung, va duong, va ung

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: hoc thieu xanh - cang thang ((va dung) OR (vat dung)) cong ((tap toan) OR (tap doan)) ban~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc thieu xanh - cang thang ((va dung) or (vat dung)) cong ((tap toan) OR (tap doan)) ban~".
• Adding a wildcard symbol may retrieve word variants: hoc thieu xanh - cang thang ((va dung) or (vat dung)) cong ((tap toan) OR (tap doan)) ban*.