Perhaps you should try some spelling variations:
cac thuc » cach thuc, cac thu, can thuc
sach duy » sach duoc, sach dao, sach dat
hieu ve » hieu va, hieu van
dan dai » dat dai, can dai, dan dat
thuc ca » thuc cua, thuc can, thuc cao
ca dan » cac dan, ca dao
cua te » cua tu
ve cac » va cac, vien cac
ma hoi » mai hoi, ma hoa, me hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sach duy) OR (sach dung)) sang ((ma hoi) or (xa hoi)). hieu ve cac thuc ca dan dai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach duy) OR (sach dung)) sang ((ma hoi) OR (xa hoi)). hieu ve cac thuc ca dan dai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sach duy) OR (sach dung)) sang ((ma hoi) or (xa hoi)). hieu ve cac thuc ca dan dai cua te".
• Adding a wildcard symbol may retrieve word variants: su ((sach duy) OR (sach dung)) sang ((ma hoi) or (xa hoi)). hieu ve cac thuc ca dan dai cua te*.