Perhaps you should try some spelling variations:
ban thanh » ban hang
cach dua » cach cua, cach dung, cac du
hoai cua » hoi cua, hoa cua, hai cua
ban hanh » ban hang
tu sach » thu sach, su sach, te sach
va cach » va cac
sach ly » sach y, sach lo, sach ty
hieu va » lieu va, hieu qua
ly nang » ky nang, ly hang, ly vang
cua tre » cua te, cuu tre, cua triet
o hoi » co hoi, o hoc, o hai
x hoi » xa 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 ly nang ((x hoi) OR (o hoi)). hieu va cach dua ((ban thanh) or (ban hanh)) hoai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ly nang ((x hoi) OR (o hoi)). hieu va cach dua ((ban thanh) OR (ban hanh)) hoai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ly nang ((x hoi) OR (o hoi)). hieu va cach dua ((ban thanh) or (ban hanh)) hoai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ly nang ((x hoi) OR (o hoi)). hieu va cach dua ((ban thanh) or (ban hanh)) hoai cua tre*.