Perhaps you should try some spelling variations:
sach van » sach han, sach va, bach van
van nang » van quang, van ban, van dong
van hanh » van thanh, ban hanh, van anh
truc van » truc va, thuc van, truc ban
cac truc » cau truc, cac tru, cac trung
su sach » so sach, vu sach
hanh de » hanh ve, hanh kem
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
ve cac » va cac, vien cac
co dai » co dan, do dai
co hai » co hoi, so hai, cong hai
de cua » le cua, te cua, dieu cua
o hai » so hai, o lai, _ hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach van nang ((((co hai) OR (co dai))) or (o hai)). hieu ve cac truc van hanh de cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach van nang ((((co hai) OR (co dai))) OR (o hai)). hieu ve cac truc van hanh de cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach van nang ((((co hai) OR (co dai))) or (o hai)). hieu ve cac truc van hanh de cua tre*".