Perhaps you should try some spelling variations:
sach van » sach han, sach va, bach van
cau thuc » cuu thuc, can thuc, cau phuc
van hanh » van thanh, van anh, van minh
ban hanh » ban hang
so sach » so sanh, bo sach, co sach
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
de cua » le cua, te cua, dieu cua
ban x » ban xu, ban _, ban 1
x hoi » xa hoi, o hoi, x ho

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: so sach van ban x hoi. hieu ve ((cau thuc) or (cau truc)) ((van hanh) OR (ban hanh)) de cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach van ban x hoi. hieu ve ((cau thuc) OR (cau truc)) ((van hanh) OR (ban hanh)) de cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach van ban x hoi. hieu ve ((cau thuc) or (cau truc)) ((van hanh) OR (ban hanh)) de cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach van ban x hoi. hieu ve ((cau thuc) or (cau truc)) ((van hanh) OR (ban hanh)) de cua tre*.