Perhaps you should try some spelling variations:
tang thanh » dang thanh, trung thanh, hoang thanh
thanh tai » thanh hai, thanh toan, doanh tai
hieu van » hieu va, thien van, lieu va
duc tang » duc thang, duc tan, tuc tang
te sach » toc sach
su sach » so sach, vu sach
van bao » van ban, van dao
bao duc » dao duc, bao luc, cao duc
tai cua » thai cua, tai cuc, tri cua
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
nang o » nang co, nang ho, nang ro
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) or (su sach)) y nang o hoi. hieu van bao duc tang thanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (su sach)) y nang o hoi. hieu van bao duc tang thanh tai cua tre.
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (su sach)) y nang o hoi. hieu van bao duc tang thanh tai cua tre*.