Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
cam thuc » am thuc, nam thuc, cam thu
sach duy » sach dung, sach duoc, sach dao
van cam » van nam, van lam, van cau
su sach » so sach, vu sach
sang ma » nang ma, sang tao, mang may
tang ma » mang may, tang van
va dan » ca dan, va dao, va dap
va dau » va dao
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) or (tang ma)) hoi. hieu van cam thuc ((va dan) OR (va dau)) dai cua te~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach duy ((sang ma) OR (tang ma)) hoi. hieu van cam thuc ((va dan) OR (va dau)) dai cua te.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach duy ((sang ma) or (tang ma)) hoi. hieu van cam thuc ((va dan) OR (va dau)) dai cua te".
• Adding a wildcard symbol may retrieve word variants: su sach duy ((sang ma) or (tang ma)) hoi. hieu van cam thuc ((va dan) OR (va dau)) dai cua te*.