Perhaps you should try some spelling variations:
vanh dai » van dai, vanh tai, van dao
nam thuc » nam thuoc, am thuc, nam thu
vu sach » vu bach, su sach, vu khach
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
sach v » sach va, sach y, sach 2
ve nam » he nam, va nam, le nam
v nang » va nang, vu nang, van nang
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: vu sach v nang ((xa hoi) or (o hoi)). hieu ve nam thuc vat ((vanh dai) OR (lanh dao)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach v nang ((xa hoi) OR (o hoi)). hieu ve nam thuc vat ((vanh dai) OR (lanh dao)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach v nang ((xa hoi) or (o hoi)). hieu ve nam thuc vat ((vanh dai) OR (lanh dao)) cua tre".
• Adding a wildcard symbol may retrieve word variants: vu sach v nang ((xa hoi) or (o hoi)). hieu ve nam thuc vat ((vanh dai) OR (lanh dao)) cua tre*.