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
su sach » so sach, vu sach
sach tu » sach thu, cach tu, sach ty
cua tre » cua te, cua triet, dua tren
duc ban » duc tan, duc van, dua ban
cau duc » cao duc, cau luc, chu duc
van cau » van dau, van hau, van chat
tu nang » tru nang, tu nong, tu nano
cuu tre » cau tren, cau treo
x hoi » o hoi, x ho, 5 hoi

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 tu nang ((x hoi) OR (xa hoi)). hieu van cau duc ban thanh vi ((cua tre) or (cuu tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach tu nang ((x hoi) OR (xa hoi)). hieu van cau duc ban thanh vi ((cua tre) OR (cuu tre)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach tu nang ((x hoi) OR (xa hoi)). hieu van cau duc ban thanh vi ((cua tre) or (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: su sach tu nang ((x hoi) OR (xa hoi)). hieu van cau duc ban thanh vi ((cua tre) or (cuu tre))*.