Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
vai cua » dai cua, hai cua, lai cua
dan vai » dan va, dan tai, dan vat
cac toc » cac toi, cac nuoc, cac thoi
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu van
tang ma » tang van
toc va » hoc va, toc ta, tuc va
va dan » ca dan, va dao, va dau

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: tu sach ky ((tang ma) OR (mang may)) hoi. ((hieu ve) OR (hieu va)) cac toc va dan vai cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((tang ma) OR (mang may)) hoi. ((hieu ve) or (hieu va)) cac toc va dan vai cua tre~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((tang ma) OR (mang may)) hoi. ((hieu ve) or (hieu va)) cac toc va dan vai cua tre*.