Perhaps you should try some spelling variations:
van viet » san viet, gian viet, tran viet
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
cao hoi » cau hoi, co hoi, cao hoc
hieu ve » hieu van
hieu va » lieu va, hieu qua
cam duc » cam xuc, cao duc, pham duc
va danh » va dinh, va hanh, dia danh
va dan » ca dan, va dao, va dau

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 cao hoi. ((hieu ve) or (hieu va)) cam duc ((va danh) or (va dan)) vi van viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky nang cao hoi. ((hieu ve) OR (hieu va)) cam duc ((va danh) OR (va dan)) vi van viet.
• Adding a wildcard symbol may retrieve word variants: su sach ky nang cao hoi. ((hieu ve) or (hieu va)) cam duc ((va danh) or (va dan)) vi van viet*.