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 va » thuc vat, thuc dan, thuc day
va dan » ca dan, va dao, va dau
va cuu » va chu, va huu
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 lang xa hoi. ((hieu va) or (lieu va)) nam thuc va dan ((va cuu) OR (va cau)) 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 va dan ((va cuu) OR (va cau)) tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky lang xa hoi. ((hieu va) or (lieu va)) nam thuc va dan ((va cuu) OR (va cau)) tre".
• Adding a wildcard symbol may retrieve word variants: toc sach ky lang xa hoi. ((hieu va) or (lieu va)) nam thuc va dan ((va cuu) OR (va cau)) tre*.