Perhaps you should try some spelling variations:
toc sach » hoc sach, doc sach, thuoc sach
nam thuc » nam thuoc, am thuc, nam thu
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang
hieu va » hieu qua
sach ky » sac ky, sach y, sach ty
thuc ca » thuc cua, thuc can, thuc cao
ca dan » cac dan, ca dao
va cuu » va cau, va huu
va chu » va che, va cau, va chi

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 lang xa hoi. ((hieu va) or (lieu va)) nam thuc ca dan ((va cuu) or (va chu)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky lang xa hoi. ((hieu va) OR (lieu va)) nam thuc ca dan ((va cuu) OR (va chu)) tre.
• Adding a wildcard symbol may retrieve word variants: toc sach ky lang xa hoi. ((hieu va) or (lieu va)) nam thuc ca dan ((va cuu) or (va chu)) tre*.