Perhaps you should try some spelling variations:
thien van » thi van
hanh than » hanh han, hanh nhan, hanh phan
than cua » nhan cua, thai cua, ban cua
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
cac duc » cao duc, cac dac, cac nuoc
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
o lai » o lao

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 ky nang o lai. ((hieu ve) or (thien van)) ((cac duc) OR (cac du)) van hanh than cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang o lai. ((hieu ve) OR (thien van)) ((cac duc) OR (cac du)) van hanh than cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang o lai. ((hieu ve) or (thien van)) ((cac duc) OR (cac du)) van hanh than cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang o lai. ((hieu ve) or (thien van)) ((cac duc) OR (cac du)) van hanh than cua tre*.