Perhaps you should try some spelling variations:
hanh tranh » canh tranh, hanh trinh, hanh trang
nhung cong » thong cong, hang cong, nhung don
hien xanh » hien hanh, hien nhanh, chieu xanh
dung cong » dung trong
tranh va » tranh van, trang va, trinh va
tan toan » tan tran, van toan, dan toan
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 tranh va ((nhung cong) OR (dung cong)) ((tan toan) OR (tap toan)) tap~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc hien xanh - hanh tranh va ((nhung cong) OR (dung cong)) ((tan toan) or (tap toan)) tap~".
• Adding a wildcard symbol may retrieve word variants: hoc hien xanh - hanh tranh va ((nhung cong) OR (dung cong)) ((tan toan) or (tap toan)) tap*.