Perhaps you should try some spelling variations:
su sach » so sach, vu sach
ly hang » ly quang
ly vang » ly van, ly quang
hieu ve » hieu va, hieu van
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
ve cac » va cac, vien cac
cac tu » cac thu, cach tu, cac du
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 hang) or (ly vang)) ((o hoi) or (x ho)). hieu ve cac tu va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ((ly hang) OR (ly vang)) ((o hoi) OR (x ho)). hieu ve cac tu va hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach ((ly hang) or (ly vang)) ((o hoi) or (x ho)). hieu ve cac tu va hanh vi cua tre*.