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