Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
hanh lai » hanh lam, hanh tai, thanh lap
vien cac » vien bach, vien dai, vien da
lai cua » dai cua, hai cua, lai chau
va hanh » van hanh, va thanh, va danh
cac xuc » cam xuc, cac nuoc, chat xuc
tu sach » thu sach, su sach, te sach
mai hoi » mai khoi, dai hoi, lai hoi
ky dang » ky nang, ky danh
ky sang » ky nang, ky tang, duy sang
cua tre » cua te, cuu tre, cua triet
xuc va » duc va, tuc va, luc 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 sang) or (ky dang)) ((mai hoi) or (xa hoi)). hieu vien cac xuc va hanh lai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((ky sang) OR (ky dang)) ((mai hoi) OR (xa hoi)). hieu vien cac xuc va hanh lai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sach ((ky sang) or (ky dang)) ((mai hoi) or (xa hoi)). hieu vien cac xuc va hanh lai cua tre*.