Perhaps you should try some spelling variations:
ban thanh » ban hang
cach dua » cach dung, cac du, cach de
cach cua » mach cua, cac cua, canh cua
ban hanh » ban hang
hoai cua » hoi cua, hoa cua, hai 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
x hoi » xa hoi, o hoi, x ho

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