Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
tang xa » trang xa, tang ma, lang xa
hieu va » lieu va, hieu qua
sach ky » sac ky, sach ty, sach kem
thuc ca » thuc cua, thuc can, thuc cao
vai cau » van cau, vai cac, lai chau
va nam » van nam, ha nam, va nay
ca dan » cac dan, ca dao
va cau » van cau, va cac, 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: toc ((sach ky) OR (sach y)) tang xa hoi. hieu va nam thuc ca dan ((vai cau) or (va cau)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc ((sach ky) OR (sach y)) tang xa hoi. hieu va nam thuc ca dan ((vai cau) OR (va cau)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc ((sach ky) OR (sach y)) tang xa hoi. hieu va nam thuc ca dan ((vai cau) or (va cau)) tren".
• Adding a wildcard symbol may retrieve word variants: toc ((sach ky) OR (sach y)) tang xa hoi. hieu va nam thuc ca dan ((vai cau) or (va cau)) tren*.