Perhaps you should try some spelling variations:
nam thuc » nam thuoc, nam thu, nam tu
cau tren » cu tren, dau tren, ca tren
vu sach » vu bach, su sach, vu khach
sach ky » sac ky, sach y, sach ty
ky sang » ky nang, ky dang, ky tang
hieu ve » hieu va, hieu van
ma hoi » mai hoi, ma hoa, me hoi
dao ca » dao cac, dao cao, dao cau
ca cau » cua cau, cac cau, can cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ky sang ((ma hoi) or (xa hoi)). hieu ve ((nam thuc) or (am thuc)) ca dao ca cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky sang ((ma hoi) OR (xa hoi)). hieu ve ((nam thuc) OR (am thuc)) ca dao ca cau tren.
• Adding a wildcard symbol may retrieve word variants: vu sach ky sang ((ma hoi) or (xa hoi)). hieu ve ((nam thuc) or (am thuc)) ca dao ca cau tren*.