Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
kho tang » cao tang
vat cua » mat cua, bat cua, dat cua
dan vat » dang vat, van vat, dan va
cac tho » cac thoi, cac tro, cac thu
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu van
ky tang » ky nang, ky dang, ky trong
tho va » tho van, tao va, tho ca
va dan » ca dan, va dao, va dau

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 tho va dan vat 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 tho va dan vat 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 tho va dan vat cua tre*".