Perhaps you should try some spelling variations:
hang vai » hang tai, hang hai, hang vi
tu sach » thu sach, su sach, te sach
duc ban » duc tan, duc van, dua ban
cac duc » cac du, cao duc, cac dac
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
vu sach » vu bach, su sach, vu khach
y nang » ky nang, ly nang, v nang
ve cac » va cac, vien cac
x hoi » xa hoi, o hoi, x ho

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