Perhaps you should try some spelling variations:
hieu cua » hieu qua, dieu cua, bieu cua
van hanh » van thanh, ban hanh, van anh
so sach » so sanh, bo sach, co sach
sach ty » sach y, sach tu, sach thu
xang xa » lang xa, mang xa, ang xa
cac duc » cac du, cac dac, cac nuoc
cao duc » dao duc, cao suc, giao duc
cua tre » cuu tre, cua triet, dua tren
cua te » cua tu

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: so sach ty xang xa hoi. hieu cua ((cac duc) OR (cao duc)) van hanh vi ((cua tre) OR (cua te))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ty xang xa hoi. hieu cua ((cac duc) OR (cao duc)) van hanh vi ((cua tre) or (cua te))~".
• Adding a wildcard symbol may retrieve word variants: so sach ty xang xa hoi. hieu cua ((cac duc) OR (cao duc)) van hanh vi ((cua tre) or (cua te))*.