Perhaps you should try some spelling variations:
luong cong » dung cong, trong cong, tong cong
hanh tran » hanh trang, thanh tran, hanh tram
tran nang » tra nang, tran dang, tran quang
cong cong » cong dong, trong cong, dung cong
tap toan » tap doan, tap quan, bai toan
toan cau » toan cao, toan ban, toan tap

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: ((25 trieu) OR (30 trieu)) tinh - hanh tran nang ((luong cong) OR (cong cong)) tap toan cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((25 trieu) or (30 trieu)) tinh - hanh tran nang ((luong cong) OR (cong cong)) tap toan cau~".
• Adding a wildcard symbol may retrieve word variants: ((25 trieu) or (30 trieu)) tinh - hanh tran nang ((luong cong) OR (cong cong)) tap toan cau*.