Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
cua viet » ca viet, hoa viet, cua vat
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang o » nang co, nang ho, nang ro
ve bac » ve bao, ve cac, ve ban
so van » su van, vo van
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 ky nang o hoi. hieu ((ve bac) or (te bao)) so van hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang o hoi. hieu ((ve bac) OR (te bao)) so van hanh vi cua viet.
• Adding a wildcard symbol may retrieve word variants: su sach ky nang o hoi. hieu ((ve bac) or (te bao)) so van hanh vi cua viet*.