Perhaps you should try some spelling variations:
hang vai » hang va, hang tai, hang hai
tu sach » thu sach, su sach, te sach
vai cua » dai cua, hai cua, lai cua
duc van » duc va, duc tan, duc manh
duc ban » duc tan, dua ban, duc man
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
sach v » sach va, sach y, sach 2
v nang » va nang, vu nang, van nang
ve cac » va cac, vien cac
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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 v nang ((x hoi) or (o hoi)). hieu ve cac ((duc ban) OR (duc van)) hang vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach v nang ((x hoi) OR (o hoi)). hieu ve cac ((duc ban) OR (duc van)) hang vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach v nang ((x hoi) or (o hoi)). hieu ve cac ((duc ban) OR (duc van)) hang vai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach v nang ((x hoi) or (o hoi)). hieu ve cac ((duc ban) OR (duc van)) hang vai cua tre*.