Perhaps you should try some spelling variations:
thanh tai » thanh hai, thanh toan, doanh tai
ban thanh » ban hanh, ban hang
dau tren » dau tien, dat tren, dau tieng
hieu van » hieu va, thien van, lieu va
van cac » van hac, van cau, van bac
sach ky » sac ky, sach y, sach ty
cac xuc » cam xuc, cac nuoc, chat xuc
xuc ban » duc ban, cuc ban, quoc ban
tai dau » tac dau, tai du, thi dau
tu sach » thu sach, su sach, te sach
o hai » co hai, so hai, _ hai
o lai » o lao
o hoi » co hoi, o hoc, o hoa

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 hoi) or (((o hai) or (o lai)))). hieu van cac xuc ban thanh tai dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (((o hai) OR (o lai)))). hieu van cac xuc ban thanh tai dau tren.
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) or (((o hai) or (o lai)))). hieu van cac xuc ban thanh tai dau tren*.