Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien da » vien dai, hien dai
vuc van » duc van, luc van, thuc van
xanh di » vanh dai, xanh tai
danh di » danh du, danh dien, danh gia
cua tre » cua te, cuu tre, cua triet
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky
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 sac ky nang ((x hoi) or (xa hoi)). hieu vien da vuc van ((xanh di) OR (danh di)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky nang ((x hoi) OR (xa hoi)). hieu vien da vuc van ((xanh di) OR (danh di)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky nang ((x hoi) or (xa hoi)). hieu vien da vuc van ((xanh di) OR (danh di)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sac ky nang ((x hoi) or (xa hoi)). hieu vien da vuc van ((xanh di) OR (danh di)) cua tre*.