Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
su sach » so sach, vu sach
cac duc » cac du, cao duc, cac dac
vai cua » dai cua, hai cua, lai cua
hieu va » lieu va, hieu qua
ty hang » ly hang, ty xang, thi hang
ty nang » ky nang, ty xang, ly nang
cua tre » cua te, cuu tre, cua triet

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ((ty nang) OR (ty hang)) xa hoi. hieu va cac duc ((ban thanh) or (ngan hang)) vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ty nang) OR (ty hang)) xa hoi. hieu va cac duc ((ban thanh) OR (ngan hang)) vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ((ty nang) OR (ty hang)) xa hoi. hieu va cac duc ((ban thanh) or (ngan hang)) vai cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ((ty nang) OR (ty hang)) xa hoi. hieu va cac duc ((ban thanh) or (ngan hang)) vai cua tre*.