Perhaps you should try some spelling variations:
hien xanh » hien hanh, hien nhanh, chieu xanh
hanh dung » thanh dung, anh dung, hanh dong
tong cong » trong cong, cong cong, dung cong
van thanh » ban thanh, van tuan
dung cua » dung luan, dung cho
cua tong » cua cong, cua dong, cua nong
tap toan » tap doan, bai toan
tap quan » tac quan, hai quan

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 cua tong cong ((van thanh) OR (((tap toan) OR (tap quan)))) cau~.
• Adding a wildcard symbol may retrieve word variants: hoc hien xanh - hanh dung cua tong cong ((van thanh) or (((tap toan) or (tap quan)))) cau*.