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