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, ban hanh, van anh
so sach » so sanh, bo sach, co sach
hieu ve » hieu va, hieu van
hanh de » hanh ve, hanh kem
cuu tre » cua tre, cau tren, cau treo
ban xu » ban tu, ban su, han xu
de cuu » de cua
ban x » ban _, ban 1, ban 2

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