Perhaps you should try some spelling variations:
tan thanh » tran thanh, tang thanh, toan thanh
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
thi van » thi lan, thi hanh, thi nang
bao duc » dao duc, bao luc, cao duc
san cua » sang cua, ban cua, dan 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: tu sach y nang o hoi. ((hieu va) or (((thien van) OR (thi van)))) bao duc tan thanh san cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang o hoi. ((hieu va) OR (((thien van) OR (thi van)))) bao duc tan thanh san cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang o hoi. ((hieu va) or (((thien van) OR (thi van)))) bao duc tan thanh san cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang o hoi. ((hieu va) or (((thien van) OR (thi van)))) bao duc tan thanh san cua tre*.