Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
tinh van » trinh van, tinh va, tich van
qua cac » cua cac
cac tuc » cac toc, cac tu, cac tac
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
tuc va » thuc va, truc va, tuc xa
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: thu sach y nang ((x hoi) or (o hoi)). hieu qua cac tuc va ((tinh van) OR (dinh van)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach y nang ((x hoi) OR (o hoi)). hieu qua cac tuc va ((tinh van) OR (dinh van)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach y nang ((x hoi) or (o hoi)). hieu qua cac tuc va ((tinh van) OR (dinh van)) cua tre".
• Adding a wildcard symbol may retrieve word variants: thu sach y nang ((x hoi) or (o hoi)). hieu qua cac tuc va ((tinh van) OR (dinh van)) cua tre*.