Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hanh hai » thanh hai, nhanh hai, hang hai
hai cua » thai cua, dai cua, hoi cua
hieu ve » hieu va, hieu van
y nang » ky nang, ly nang, v nang
ve cac » va cac, vien cac
xac va » tac va, ac va, bac va
cua te » cua tu
o hoc » co hoc, mo hoc, so hoc
o hoi » co hoi, o hai, o hoa

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: thu sach y nang ((o hoi) OR (o hoc)). hieu ve cac ((xac va) OR (duc va)) hanh hai cua te~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach y nang ((o hoi) OR (o hoc)). hieu ve cac ((xac va) or (duc va)) hanh hai cua te~".
• Adding a wildcard symbol may retrieve word variants: thu sach y nang ((o hoi) OR (o hoc)). hieu ve cac ((xac va) or (duc va)) hanh hai cua te*.