Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
danh vai » danh sai, danh va, doanh van
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
vai cua » dai cua, hai cua, lai cua
cua tre » cua te, cuu tre, cua triet
x hoi » xa hoi, o hoi, 5 hoi
bo va » bao va, so va, co va
do va » do van, so va

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