Perhaps you should try some spelling variations:
hien xanh » hien hanh, hien nhanh, chieu xanh
hanh dung » thanh dung, anh dung, manh dung
hanh dong » anh dong, ha dong
tong cong » trong cong, cong cong, dung cong
cua tong » cua cong, cua dong, cua nong
van toan » van tuan, van tan, van thanh
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: hoc hien xanh - ((hanh dung) OR (hanh dong)) cua tong cong ((van toan) OR (tap toan)) cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc hien xanh - ((hanh dung) OR (hanh dong)) cua tong cong ((van toan) or (tap toan)) cau~".
• Adding a wildcard symbol may retrieve word variants: hoc hien xanh - ((hanh dung) OR (hanh dong)) cua tong cong ((van toan) or (tap toan)) cau*.