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