Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
va hanh » van hanh, va thanh, va danh
cac thu » cach thuc, cac thoi
van cac » van hac, van cau, van bac
cua tre » cua te, cuu tre, cua triet
ly nang » ky nang, ly hang, ly quang
ly vang » ly hang, ly van, ly quang
thu va » thuc va, thue va, tu va
vi cua » vai cua, di cua
o hoi » co hoi, o hoc, o hai

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