Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
thuc ban » thuoc ban, thuc dan, thu ban
cam thuc » am thuc, nam thuc, cam thu
mang xa » lang xa, mang may, dang xay
van cam » van nam, van lam, van cau
sach ty » sach y, sach tu, sach thu
xang xa » lang xa, ang xa, dang xay
te sach » toc sach
va cao » va cac, va co, va dao
va ca » va cac, va cai, va cau

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ty ((xang xa) or (mang xa)) hoi. hieu van cam thuc ban thanh ((va ca) or (va cao)) viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty ((xang xa) OR (mang xa)) hoi. hieu van cam thuc ban thanh ((va ca) OR (va cao)) viet.
• Adding a wildcard symbol may retrieve word variants: te sach ty ((xang xa) or (mang xa)) hoi. hieu van cam thuc ban thanh ((va ca) or (va cao)) viet*.