Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam thu
so sach » so sanh, bo sach, hoc sach
co sach » bo sach, cuon sach, hoc sach
thuc va » thuc vat, thuc dan, thuc day
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di 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) OR (co sach))) OR (toc sach)) ky nang x hoi. hieu van nam thuc va hanh vi cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((so sach) OR (co sach))) or (toc sach)) ky nang x hoi. hieu van nam thuc va hanh vi cua tre~".
• Adding a wildcard symbol may retrieve word variants: ((((so sach) OR (co sach))) or (toc sach)) ky nang x hoi. hieu van nam thuc va hanh vi cua tre*.