Perhaps you should try some spelling variations:
nang mai » nang ma, nang tai, lang mai
hieu van » hieu va, thien van, lieu va
cua viet » ca viet, cua vat, cua dieu
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
hieu ve » hieu va
va hanh » van hanh, va thanh, va danh
thu va » thuc va, thue va, tu va

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: su sach ky nang mai hoi. ((hieu ve) OR (hieu van)) nam thu va hanh vi ((cua viet) OR (hoa viet))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky nang mai hoi. ((hieu ve) OR (hieu van)) nam thu va hanh vi ((cua viet) or (hoa viet))~".
• Adding a wildcard symbol may retrieve word variants: su sach ky nang mai hoi. ((hieu ve) OR (hieu van)) nam thu va hanh vi ((cua viet) or (hoa viet))*.