Perhaps you should try some spelling variations:
canh trinh » canh tranh, hanh trinh, canh tinh
trinh dan » trinh han, trinh san, trinh da
nang cong » nang song, bang cong, hang cong
dang cong » dung cong
theo chu » theo chieu, cho chu, chao chu
chu sach » cau sach, thu sach, chieu sach
dan toan » van toan, manh toan, xuan toan
dan than » dan chan, ban than, van than

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: theo chu sach - canh trinh dan ((nang cong) OR (dang cong)) ((dan toan) OR (dan than)) cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "theo chu sach - canh trinh dan ((nang cong) or (dang cong)) ((dan toan) OR (dan than)) cau~".
• Adding a wildcard symbol may retrieve word variants: theo chu sach - canh trinh dan ((nang cong) or (dang cong)) ((dan toan) OR (dan than)) cau*.