Perhaps you should try some spelling variations:
duc ngan » duc ngon, duc nhan, luc ngan
hang vai » hang va, hang tai, hang hai
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
cac duc » cac du, cac dac, cao duc
vai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
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 y nang ((x ho) or (o hoi)). hieu ve cac duc ngan hang vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((x ho) OR (o hoi)). hieu ve cac duc ngan hang vai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((x ho) or (o hoi)). hieu ve cac duc ngan hang vai cua tre*.