Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
cua viet » ca viet, cua vat, cua dieu
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
va ban » van ban, va bai, va bao
ban so » ban do, ban co, ban bo
so van » su van, vo van

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang x ho. hieu va ban so van hanh vi ((cua viet) OR (hoa viet))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang x ho. hieu va ban so van hanh vi ((cua viet) OR (hoa viet))".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang x ho. hieu va ban so van hanh vi ((cua viet) OR (hoa viet))*.