Perhaps you should try some spelling variations:
thien van » thi van
hanh vai » hanh vi, hanh va, hanh tai
hieu van » hieu va, lieu va, hieu ve
te sach » toc sach
vai cua » dai cua, hai cua, lai cua
sach ty » sach y, sach tu, sach thu
ty hang » ly hang, ty xang, thi hang
cua tre » cua te, cuu tre, cua triet
bo van » vo van, do van, ho van
so van » su van, vo van
hang o » hang do, hang o2, hoang o
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 ty hang o hoi. ((hieu van) or (thien van)) cac ((bo van) or (so van)) hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty hang o hoi. ((hieu van) OR (thien van)) cac ((bo van) OR (so van)) hanh vai cua tre.
• Adding a wildcard symbol may retrieve word variants: te sach ty hang o hoi. ((hieu van) or (thien van)) cac ((bo van) or (so van)) hanh vai cua tre*.