Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
cam thuc » am thuc, nam thuc, cam thu
va trien » va truyen, va tuyen, va tieng
thanh vu » thanh va, thanh ve, thanh tu
lang van » dang van, tang van, hoang van
thuc ban » thuoc ban, thuc dan, thu ban
su sach » so sach, vu sach
van cam » van nam, van lam, van cau
lang xa » lang ha, dang xay
sach o » sach lo, sac o, sach y
thiet » thieu

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 o ((lang xa) or (lang van)) hoi. hieu van cam thuc ban thanh vu ((va trien) OR (va thiet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach o ((lang xa) OR (lang van)) hoi. hieu van cam thuc ban thanh vu ((va trien) OR (va thiet))*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach o ((lang xa) or (lang van)) hoi. hieu van cam thuc ban thanh vu ((va trien) OR (va thiet))*".