Perhaps you should try some spelling variations:
thieu xanh » chieu xanh, hieu manh, thien anh
hanh tang » hanh trang, hanh mang, hanh tung
dung cong » dung trong
anh tang » anh bang, anh dang, anh nang
cua dung » cua dang, cua dong, qua dung
bai toan » bai tap
van tan » van tuan, van ban, van tai

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: toc thieu xanh - ((hanh tang) OR (anh tang)) cua dung cong ((bai toan) OR (van tan)) cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc thieu xanh - ((hanh tang) OR (anh tang)) cua dung cong ((bai toan) or (van tan)) cau~".
• Adding a wildcard symbol may retrieve word variants: toc thieu xanh - ((hanh tang) OR (anh tang)) cua dung cong ((bai toan) or (van tan)) cau*.