Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
su sach » so sach, vu sach
van cac » van hac, van cau, van bac
cac van » cac dan
luu tre » luu tru, cuu tre, luy tre
nang o » nang co, nang ho, nang ro
vi luu » vi lua
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: ((toc sach) or (su sach)) ky nang o hoi. hieu van cac ((cua ban) or (cac van)) hanh vi luu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (su sach)) ky nang o hoi. hieu van cac ((cua ban) OR (cac van)) hanh vi luu tre.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (su sach)) ky nang o hoi. hieu van cac ((cua ban) or (cac van)) hanh vi luu tre*.