Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
thanh va » thanh van, hanh va, thanh ha
hieu van » hieu va, thien van, lieu va
van hac » van hoc, van ha, van hai
sach tu » sach thu, cach tu, sach uu
dat ban » bat ban, da ban, day ban
hac dat » hoc dat, tac dat, hoach dat
sach ty » sach y, sach thu, xach tay
va cua » va chua, via cua, ca cua
ma hoi » mai hoi, ma hoa, me hoi

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu ((sach ty) or (sach tu)) nang ((ma hoi) or (xa hoi)). hieu van hac dat ban thanh va cua vat~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ty) OR (sach tu)) nang ((ma hoi) OR (xa hoi)). hieu van hac dat ban thanh va cua vat.
• Adding a wildcard symbol may retrieve word variants: tu ((sach ty) or (sach tu)) nang ((ma hoi) or (xa hoi)). hieu van hac dat ban thanh va cua vat*.