Perhaps you should try some spelling variations:
ban thanh » ban hanh
ban hang » ngan hang
ky tang » ky nang, ky dang, kho tang
hieu ve » hieu va, hieu van
cac duc » cac du, cao duc, cac dac
cua tre » cua te, cuu tre, cua triet
su sac » su sach, su cac, su xac
sac ky » cac ky, sai ky
ve cac » va cac, vien cac

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

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