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
hieu va » lieu va, hieu qua
ky lang » ky nang, ky dang, ky tang
sach ky » sac ky, sach y, sach ty
vai cau » van cau, vai cac, lai chau
va nam » van nam, ha nam, va nay
va dao » ca dao
va cau » van cau, va cac, va dau
va dan » ca dan, va dau, va dap

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 nam thuc ((va dan) or (va dao)) ((vai cau) OR (va cau)) tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: toc sach ky lang xa hoi. hieu va nam thuc ((va dan) OR (va dao)) ((vai cau) OR (va cau)) tren.
• The words AND, OR and NOT may confuse the search; try adding quotes: "toc sach ky lang xa hoi. hieu va nam thuc ((va dan) or (va dao)) ((vai cau) OR (va cau)) tren".
• Adding a wildcard symbol may retrieve word variants: toc sach ky lang xa hoi. hieu va nam thuc ((va dan) or (va dao)) ((vai cau) OR (va cau)) tren*.