Perhaps you should try some spelling variations:
hoc sach » hoc sinh, hoc cac, hoc anh
hieu van » hieu va, thien van, lieu va
so sach » bo sach, co sach
tinh va » tich va, trinh van, trinh vat
duc may » duc mau, duc man, duc manh
lam duc » lam duoc, pham duc, nam duoc
van lam » van nam
cua tre » cua te, cuu tre, cua triet
so sanh » do sanh
va cua » va chua, via cua, ca cua
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) OR (so sanh))) or (hoc sach)) ky nang x hoi. hieu van lam duc may tinh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((((so sach) OR (so sanh))) OR (hoc sach)) ky nang x hoi. hieu van lam duc may tinh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((so sach) OR (so sanh))) or (hoc sach)) ky nang x hoi. hieu van lam duc may tinh va cua tre".
• Adding a wildcard symbol may retrieve word variants: ((((so sach) OR (so sanh))) or (hoc sach)) ky nang x hoi. hieu van lam duc may tinh va cua tre*.