Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
cau tren » cu tren, dau tren, ca tren
tang xa » trang xa, tang ma, lang xa
hieu va » lieu va, hieu qua
ky tang » ky nang, ky dang, kho tang
sach ky » sac ky, sach y, sach ty
cuu tre » cua tre, cau treo
va nam » van nam, ha nam, va nay
va dao » 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: toc sach ky tang xa hoi. hieu va nam thuc ((va dao) or (va dau)) vai ((cuu tre) or (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky tang xa hoi. hieu va nam thuc ((va dao) OR (va dau)) vai ((cuu tre) OR (cau tren)).
• Adding a wildcard symbol may retrieve word variants: toc sach ky tang xa hoi. hieu va nam thuc ((va dao) or (va dau)) vai ((cuu tre) or (cau tren))*.