Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
cua viet » hoa viet, cua vat, cua dieu
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
vien cac » vien bach, vien dai, vien da
va hanh » van hanh, va thanh, va danh
sach tu » sach thu, cach tu, sach ty
tu sach » thu sach, su sach, te sach
lai hoi » dai hoi, lai hoa, lai roi
mai hoi » mai khoi, dai hoi, mai doi
tu nang » tru nang, tu nong, tu nano
ca viet » va viet, co viet, hoa viet

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 tu nang ((mai hoi) or (lai hoi)). hieu vien cac nuoc va hanh vi ((cua viet) OR (ca viet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach tu nang ((mai hoi) OR (lai hoi)). hieu vien cac nuoc va hanh vi ((cua viet) OR (ca viet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach tu nang ((mai hoi) or (lai hoi)). hieu vien cac nuoc va hanh vi ((cua viet) OR (ca viet))".
• Adding a wildcard symbol may retrieve word variants: tu sach tu nang ((mai hoi) or (lai hoi)). hieu vien cac nuoc va hanh vi ((cua viet) OR (ca viet))*.