Perhaps you should try some spelling variations:
thanh vai » thanh hai, thanh van, thanh tai
tan thanh » tran thanh, tang thanh, toan thanh
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
vai cua » dai cua, hai cua, lai cua
bao duc » dao duc, bao luc, cao duc
van bao » van ban, van dao
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
o lai » o lao
o hai » co hai, so hai, _ hai
o hoc » co hoc, mo hoc, so hoc

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 y nang ((((o hai) or (o lai))) or (o hoc)). hieu van bao duc tan thanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((((o hai) OR (o lai))) OR (o hoc)). hieu van bao duc tan thanh vai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((((o hai) or (o lai))) or (o hoc)). hieu van bao duc tan thanh vai cua tre*.