Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
cua tre » cua te, cuu tre, cua triet
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky
cac tu » cac thu, cach tu, cac du
dan vi » doan vi, don vi, gan vi
dan va » doan va, dan ca, ban va
x hoi » xa hoi, o hoi, 5 hoi
tu ca » tu cac, tu cua, tu can

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sac ky nang ((x hoi) OR (x ho)). hieu vien cac tu ca ((dan vi) or (dan va)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky nang ((x hoi) OR (x ho)). hieu vien cac tu ca ((dan vi) OR (dan va)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky nang ((x hoi) OR (x ho)). hieu vien cac tu ca ((dan vi) or (dan va)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sac ky nang ((x hoi) OR (x ho)). hieu vien cac tu ca ((dan vi) or (dan va)) cua tre*.