Perhaps you should try some spelling variations:
thieu xanh » hieu manh, thien anh, thien danh
chieu xanh » chieu sach, chieu sang, chieu tinh
cang thang » cong thanh, dang thanh
vat dung » van dung, viet dung, mat duong
cong tap » cuong tap, cong tac, cong tan
tap toan » tap doan, tap quan, bai toan
toan ban » van ban
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) OR (chieu xanh)) - cang thang ((va dung) OR (vat dung)) cong tap toan ban~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((thieu xanh) OR (chieu xanh)) - cang thang ((va dung) or (vat dung)) cong tap toan ban~".
• Adding a wildcard symbol may retrieve word variants: hoc ((thieu xanh) OR (chieu xanh)) - cang thang ((va dung) or (vat dung)) cong tap toan ban*.