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