Perhaps you should try some spelling variations:
va thanh » gia thanh, ban thanh, le thanh
te sach » toc sach
cac duc » cac du, cao duc, cac dac
dat cua » dai cua, day cua, mat cua
va tinh » may tinh
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
hieu ve » hieu van
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
ma hoi » mai hoi, xa hoi, ma hoa

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: te sach ky nang ma hoi. ((hieu ve) OR (hieu va)) cac duc ((va thanh) OR (va tinh)) dat cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky nang ma hoi. ((hieu ve) OR (hieu va)) cac duc ((va thanh) or (va tinh)) dat cua tre~".
• Adding a wildcard symbol may retrieve word variants: te sach ky nang ma hoi. ((hieu ve) OR (hieu va)) cac duc ((va thanh) or (va tinh)) dat cua tre*.