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

You may be able to get more results by adjusting your search query.

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