Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
cua viet » ca viet, hoa viet, cua vat
su sach » so sach, vu sach
cao hoi » cau hoi, co hoi, cao hoc
van cac » van hac, van cau, van bac
du van » duy van, duc van, tu van
vi cua » vai cua, di cua

You may be able to get more results by adjusting your search query.

• If you are trying to use Boolean operators, they must be ALL CAPS: ((toc sach) OR (su sach)) ky nang cao hoi. hieu van cac du van hanh vi cua viet~.
• Adding a wildcard symbol may retrieve word variants: ((toc sach) or (su sach)) ky nang cao hoi. hieu van cac du van hanh vi cua viet*.