Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hanh vai » hanh va, hanh tai, hanh van
su sach » vu sach
so sach » so sanh, bo sach, co sach
van cac » van hac, van cau, van bac
cua tre » cua te, cuu tre, cua triet
cac lo » cac lop, cac co, cac bo
lo van » le van, vo van, so van

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) or (so sach)) ky nang x ho. hieu van cac lo van ((hanh vai) or (hanh vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sach)) ky nang x ho. hieu van cac lo van ((hanh vai) OR (hanh vi)) cua tre.
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (so sach)) ky nang x ho. hieu van cac lo van ((hanh vai) or (hanh vi)) cua tre*.