Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
thanh va » thanh van, hanh va, thanh ha
te sach » toc sach
sach ky » sac ky, sach y, sach ty
van bao » van ban, van dao
cua tre » cua te, cuu tre, cua triet
va cua » va chua, via cua, ca cua
x hoi » xa hoi, x ho, 5 hoi
o hoi » co hoi, o hoc, o hai

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