Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
hieu van » hieu va, thien van, lieu va
va thanh » gia thanh, ban thanh, va tinh
mai hoi » mai khoi, dai hoi, lai hoi
van cac » van hac, van cau, van bac
dat cua » dai cua, day cua, dan cua
mat cua » ma cua, manh cua, mang cua
y nang » ky nang, ly nang, v nang
du va » dau va, tu va, su 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: toc sach y nang ((ma hoa) OR (mai hoi)). hieu van cac du va thanh ((dat cua) OR (mat cua)) tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach y nang ((ma hoa) or (mai hoi)). hieu van cac du va thanh ((dat cua) OR (mat cua)) tre~".
• Adding a wildcard symbol may retrieve word variants: toc sach y nang ((ma hoa) or (mai hoi)). hieu van cac du va thanh ((dat cua) OR (mat cua)) tre*.