Perhaps you should try some spelling variations:
sach nuoc » sach duoc, cac nuoc, bach tuoc
qua sach » quan sach, quoc sach, qua cac
tu sach » thu sach, su sach, te sach
va hanh » van hanh, va thanh, va danh
lai cuu » lai chau, lai cuoc, loai cua
lai cua » dai cua, hai cua, lai chau
y nang » ky nang, ly nang, v nang
x hoi » xa hoi, o hoi, 5 hoi

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: tu sach y nang ((x hoi) OR (x ho)). hieu qua sach nuoc va hanh ((lai cuu) OR (lai cua)) tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang ((x hoi) or (x ho)). hieu qua sach nuoc va hanh ((lai cuu) OR (lai cua)) tre~".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((x hoi) or (x ho)). hieu qua sach nuoc va hanh ((lai cuu) OR (lai cua)) tre*.