Perhaps you should try some spelling variations:
ban thanh » ban hanh, ban hang
thanh vi » hanh vi, thanh va, thanh ve
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
vi cua » vai cua, di 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 vi 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 vi cua vat.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ty) OR (sach tu)) nang ((ma hoi) or (xa hoi)). hieu van hac dat ban thanh vi 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 vi cua vat*.