Perhaps you should try some spelling variations:
van khanh » van thanh, van hanh, van anh
van nhanh » van thanh, van hanh, van nhan
tu sach » thu sach, su sach, te sach
thi cua » thai cua, thi cuc, tri cua
cua tre » cua te, cuu tre, cua triet
cac xuc » cam xuc, cac nuoc, chat xuc
sach ky » sac ky, sach y, sach ty
hieu ve » hieu va, hieu van
co loi » co hoi
ve cac » va cac, vien cac
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 ky nang ((o hoi) or (co loi)). hieu ve cac xuc ((van nhanh) OR (van khanh)) thi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (co loi)). hieu ve cac xuc ((van nhanh) OR (van khanh)) thi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hoi) or (co loi)). hieu ve cac xuc ((van nhanh) OR (van khanh)) thi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((o hoi) or (co loi)). hieu ve cac xuc ((van nhanh) OR (van khanh)) thi cua tre*.