Perhaps you should try some spelling variations:
va thanh » ban thanh, va tinh, le thanh
so sach » so sanh, bo sach, co sach
cac duc » cac du, cao duc, cac dac
lap cua » lai cua, tap cua, lam cua
hieu ve » hieu va, hieu van
sach ky » sac ky, sach y, sach ty
dai hoi » dai hoc, dai hai, dai moi
ky dang » ky nang, ky danh
ve cac » va cac, vien cac
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 ky dang ((dai hoi) OR (xa hoi)). hieu ve cac duc ((va thanh) OR (gia thanh)) lap cua te~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky dang ((dai hoi) or (xa hoi)). hieu ve cac duc ((va thanh) OR (gia thanh)) lap cua te~".
• Adding a wildcard symbol may retrieve word variants: so sach ky dang ((dai hoi) or (xa hoi)). hieu ve cac duc ((va thanh) OR (gia thanh)) lap cua te*.