Perhaps you should try some spelling variations:
quoc ban » quoc bao, quoc lan, quoc quan
tu sach » thu sach, su sach, te sach
cuc ban » cua ban, cac ban, cuu ban
sach ky » sac ky, sach y, sach ty
va cham » va chat, va tham
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va, hieu qua
anh da » anh dat, anh d, anh va
da cua » dai cua, day cua, dan cua
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, o hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang ((o hoi) OR (o hai)). hieu va cham ((quoc ban) or (cuc ban)) anh da cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (o hai)). hieu va cham ((quoc ban) OR (cuc ban)) anh da cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hoi) OR (o hai)). hieu va cham ((quoc ban) or (cuc ban)) anh da cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) OR (o hai)). hieu va cham ((quoc ban) or (cuc ban)) anh da cua tre*.