Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
van hanh » van thanh, ban hanh, van anh
hieu van » hieu va, thien van, lieu va
so sanh » do sanh
hanh va » hang va, hanh vi
xuc van » duc van, luc van, vuc van
nam xuc » cam xuc, nam xua, nam thuc
cua tre » cua te, cuu tre, cua triet
va cua » va chua, via cua, ca cua
x hoi » xa hoi, x ho, 5 hoi
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((so sanh) or (toc sach)) ky nang ((x hoi) OR (o hoi)). hieu van nam xuc van hanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((so sanh) OR (toc sach)) ky nang ((x hoi) OR (o hoi)). hieu van nam xuc van hanh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((so sanh) or (toc sach)) ky nang ((x hoi) OR (o hoi)). hieu van nam xuc van hanh va cua tre".
• Adding a wildcard symbol may retrieve word variants: ((so sanh) or (toc sach)) ky nang ((x hoi) OR (o hoi)). hieu van nam xuc van hanh va cua tre*.