Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
su sach » so sach, vu sach
vai cua » dai cua, hai cua, lai cua
va hanh » va thanh, va danh, ban hanh
hieu ve » hieu va
sach ky » sac ky, sach y, sach ty
cua tre » cua te, cuu tre, cua triet
cac lo » cac lop, cac co, cac bo
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: su sach ky nang x hoi. ((hieu ve) or (hieu van)) cac lo ((va hanh) OR (van hanh)) vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang x hoi. ((hieu ve) OR (hieu van)) cac lo ((va hanh) OR (van hanh)) vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang x hoi. ((hieu ve) or (hieu van)) cac lo ((va hanh) OR (van hanh)) vai cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang x hoi. ((hieu ve) or (hieu van)) cac lo ((va hanh) OR (van hanh)) vai cua tre*.