Perhaps you should try some spelling variations:
hanh trang » thanh trung, canh tranh, hanh trinh
thong tong » thong thong, thong trong, thong cong
trang cua » tranh cua, tang cua, trung cua
cua thong » cua thuong, cua khong, cua tong
ho trieu » mot trieu, 30 trieu, ho chieu
25 trieu » 30 trieu
tap toan » tap doan, tap quan
bai toan » bai 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: ((ho trieu) OR (25 trieu)) tinh - hanh trang cua thong tong ((tap toan) OR (bai toan)) cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((ho trieu) or (25 trieu)) tinh - hanh trang cua thong tong ((tap toan) OR (bai toan)) cau~".
• Adding a wildcard symbol may retrieve word variants: ((ho trieu) or (25 trieu)) tinh - hanh trang cua thong tong ((tap toan) OR (bai toan)) cau*.