Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
vat cua » mat cua, bat cua, dat cua
dan vat » dang vat, van vat, dan va
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
ky tang » ky nang, ky dang, kho tang
ma hoi » mai hoi, xa hoi, me hoi
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 hoi) OR (ma hoa)). ((hieu ve) OR (hieu va)) cac toc va dan vat cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky tang ((ma hoi) OR (ma hoa)). ((hieu ve) or (hieu va)) cac toc va dan vat cua tre~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky tang ((ma hoi) OR (ma hoa)). ((hieu ve) or (hieu va)) cac toc va dan vat cua tre*.