Perhaps you should try some spelling variations:
sach duy » sach dung, sach duoc, sach dao
duy sang » duy van, duy can, duy anh
thuc can » thuc chan, thuc dan, thuc van
cam thuc » am thuc, nam thuc, cam thu
su sach » so sach, vu sach
dan dai » dat dai, dan dat, dan da
hieu ve » hieu va, hieu van
ve cam » ve cham, ve cac, va cam
ma hoi » mai hoi, ma hoa, me hoi
cua te » cua tu

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