Perhaps you should try some spelling variations:
va thanh » gia thanh, ban thanh, va tinh
so sach » so sanh, bo sach, co sach
cac duc » cac du, cao duc, cac dac
lam cua » nam cua, lam chat
lap cua » lai cua, tap cua, ap cua
hieu ve » hieu va, hieu van
sach ky » sac ky, sach y, sach ty
mai hoi » mai khoi, dai hoi, lai hoi
ky dang » ky nang, ky danh
ve cac » va cac, vien cac

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 ((mai hoi) OR (xa hoi)). hieu ve cac duc va thanh ((lap cua) OR (lam cua)) te~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky dang ((mai hoi) or (xa hoi)). hieu ve cac duc va thanh ((lap cua) OR (lam cua)) te~".
• Adding a wildcard symbol may retrieve word variants: so sach ky dang ((mai hoi) or (xa hoi)). hieu ve cac duc va thanh ((lap cua) OR (lam cua)) te*.