Perhaps you should try some spelling variations:
sach van » sach han, sach va, bach van
van nang » van quang, van ban, van dong
ban hang » ngan hang
cau thuc » cau truc, cuu thuc, can thuc
so sach » so sanh, bo sach, co sach
hieu ve » hieu va, hieu van
ve cau » ke cau, va cau, ve cac
de cua » le cua, dieu cua
te cua » tue cua, le cua
x hoi » xa hoi, o hoi, x ho

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: so sach van nang x hoi. hieu ve cau thuc ((ban hanh) OR (ban hang)) ((de cua) OR (te cua)) tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach van nang x hoi. hieu ve cau thuc ((ban hanh) OR (ban hang)) ((de cua) or (te cua)) tre~".
• Adding a wildcard symbol may retrieve word variants: so sach van nang x hoi. hieu ve cau thuc ((ban hanh) OR (ban hang)) ((de cua) or (te cua)) tre*.