Perhaps you should try some spelling variations:
hanh vai » hanh vi, hanh va, hanh tai
va nhan » van nhan, ca nhan, va phan
vai cua » dai cua, hai cua, lai cua
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
luc va » duc va, loc va
tuc va » thuc va, truc va, tuc xa
x hoi » o hoi, x ho, 5 hoi

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 y nang ((x hoi) or (xa hoi)). hieu va nhan ((luc va) OR (tuc va)) hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((x hoi) OR (xa hoi)). hieu va nhan ((luc va) OR (tuc va)) hanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang ((x hoi) or (xa hoi)). hieu va nhan ((luc va) OR (tuc va)) hanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((x hoi) or (xa hoi)). hieu va nhan ((luc va) OR (tuc va)) hanh vai cua tre*.