Perhaps you should try some spelling variations:
thanh hai » thanh phan, thanh hoa, thanh san
ban thanh » ban hanh, ban hang
hieu van » hieu va, thien van, lieu va
tu sach » thu sach, su sach, te sach
xuc ban » duc ban, cuc ban, quoc ban
cac xuc » cam xuc, cac nuoc, chat xuc
van cac » van hac, van cau, van bac
ca tren » cau tren, cu tren, la tren
sach ky » sac ky, sach y, sach ty
so hai » son hai, su hai, so ha
hai ca » hai cua, hai ba, bai ca
o hoc » co hoc, mo hoc, so hoc
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 hoc) or (((so hai) or (o lai)))). hieu van cac xuc ban thanh hai ca tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoc) OR (((so hai) OR (o lai)))). hieu van cac xuc ban thanh hai ca tren.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoc) or (((so hai) or (o lai)))). hieu van cac xuc ban thanh hai ca tren*.