Perhaps you should try some spelling variations:
hieu quang » thieu quang, hieu quan, hieu qua
nam thuc » nam thuoc, am thuc, nam thu
dang xay » dang van, van xay
so sach » so sanh, bo sach, co sach
lang xa » lang ha, lang van
su tien » su kien, su hien, tu tieng
va dan » ca dan, va dau, va dap
va dao » ca dao
vai su » va su, van su, lai su

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach y ((lang xa) or (dang xay)) hoi. hieu quang nam thuc ((va dan) or (va dao)) vai su tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y ((lang xa) OR (dang xay)) hoi. hieu quang nam thuc ((va dan) OR (va dao)) vai su tien.
• Adding a wildcard symbol may retrieve word variants: so sach y ((lang xa) or (dang xay)) hoi. hieu quang nam thuc ((va dan) or (va dao)) vai su tien*.