Perhaps you should try some spelling variations:
hang vai » hang tai, hang hai, hang vi
tu sach » thu sach, su sach, te sach
hieu ve » hieu va, hieu van
cac duc » cac du, cao duc, cac dac
cua tre » cua te, cuu tre, cua triet
sach v » sach va, sach y, sach 2
v nang » va nang, vu nang, van nang
ve cac » va cac, vien cac
x hoi » o 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 (xa hoi)). hieu ve cac duc tan ((hang vai) or (hang va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach v nang ((x hoi) OR (xa hoi)). hieu ve cac duc tan ((hang vai) OR (hang va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach v nang ((x hoi) OR (xa hoi)). hieu ve cac duc tan ((hang vai) or (hang va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach v nang ((x hoi) OR (xa hoi)). hieu ve cac duc tan ((hang vai) or (hang va)) cua tre*.