Perhaps you should try some spelling variations:
nam thuc » nam thuoc, am thuc, nam thu
cau tren » cu tren, dau tren, ca tren
sach ty » sach y, sach tu, sach thu
lang xa » lang ha, dang xay, lang van
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach kem
vai cau » va cau, van cau, vai cac
va dan » ca dan, va dau, va dap
va dao » ca dao
va nam » van nam, ha nam, va nay

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