Perhaps you should try some spelling variations:
thanh vai » thanh hai, thanh van, thanh tai
van thanh » ban thanh, van tuan
thu sach » thuat sach, thuoc sach, thu hoach
hieu van » hieu va, thien van, lieu va
cao duc » cao suc, giao duc, tao duoc
vai cua » dai cua, hai cua, lai cua
dao duc » giao duc, tao duoc
cua tre » cua te, cuu tre, cua triet
tu sach » su sach, te sach, tu cach
nang o » nang co, nang ho, nang ro
y nang » ky nang, ly nang, v nang
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: ((thu sach) OR (tu sach)) y nang o hoi. hieu van ((cao duc) or (dao duc)) van thanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (tu sach)) y nang o hoi. hieu van ((cao duc) OR (dao duc)) van thanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) OR (tu sach)) y nang o hoi. hieu van ((cao duc) or (dao duc)) van thanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) OR (tu sach)) y nang o hoi. hieu van ((cao duc) or (dao duc)) van thanh vai cua tre*.