Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
sach ky » sac ky, sach y, sach ty
ky tang » ky nang, ky dang, kho tang
tang xa » trang xa, tang ma, lang xa
hieu va » lieu va, hieu qua
vai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet
va nam » van nam, ha nam, va nay
va dan » ca dan, va dao, va dap
va dau » va dao

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

• Performing a fuzzy search may retrieve terms with similar spellings: toc sach ky tang xa hoi. hieu va nam thuc ((va dan) or (va dau)) vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky tang xa hoi. hieu va nam thuc ((va dan) OR (va dau)) vai cua tre.
• Adding a wildcard symbol may retrieve word variants: toc sach ky tang xa hoi. hieu va nam thuc ((va dan) or (va dau)) vai cua tre*.