Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
hang vai » hang tai, hang hai, hang vi
thu sach » tu sach, thuat sach, thuoc sach
duc ban » duc tan, duc van, dua ban
cac duc » cac du, cao duc, cac dac
su sach » so sach, vu sach
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
y nang » ky nang, ly nang, v 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: ((su sach) or (thu sach)) y nang o hoi. hieu vien cac duc ban ((hang vai) or (hang va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (thu sach)) y nang o hoi. hieu vien cac duc ban ((hang vai) OR (hang va)) cua tre.
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (thu sach)) y nang o hoi. hieu vien cac duc ban ((hang vai) or (hang va)) cua tre*.