Perhaps you should try some spelling variations:
sach thu » sach thue, sach thieu, sach tham
thu nang » thi nang, thu hang, thu bang
hieu van » hieu va, thien van, lieu va
ban hanh » ban hang
te sach » toc sach
van cau » van dau, van hau, van chat
cau duc » cao duc, cau luc, chu duc
duc ban » duc tan, duc van, dua ban
hanh va » hang va, hanh vi
cua tre » cua te, cuu tre, cua triet
va cua » va chua, via cua, ca cua
x hoi » xa hoi, o hoi, x ho
o hai » co hai, so hai, o lai

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 thu nang ((x hoi) or (o hai)). hieu van cau duc ban hanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach thu nang ((x hoi) OR (o hai)). hieu van cau duc ban hanh va cua tre.
• Adding a wildcard symbol may retrieve word variants: te sach thu nang ((x hoi) or (o hai)). hieu van cau duc ban hanh va cua tre*.