Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
kho tang » cao tang
vai cua » dai cua, hai cua, lai cua
dan vai » dan va, dan tai, dan vat
hieu va » lieu va, hieu qua
hieu ve » hieu van
ky tang » ky nang, ky dang, ky trong
cua tre » cua te, cuu tre, cua triet
tro ca » tro cua, tro cap, tho ca
ca dan » cac dan, ca dao

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: thu sach ((ky tang) OR (kho tang)) ma hoa. ((hieu ve) or (hieu va)) cac tro ca dan vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((ky tang) OR (kho tang)) ma hoa. ((hieu ve) OR (hieu va)) cac tro ca dan vai cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ((ky tang) OR (kho tang)) ma hoa. ((hieu ve) or (hieu va)) cac tro ca dan vai cua tre*".