Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
hanh vai » hanh vi, hanh va, hanh tai
duc van » duc va, duc tan, duc manh
vai cua » dai cua, hai cua, lai cua
hoc can » hoc dan, hoc cao, hoc cac
cua tre » cua te, cuu tre, cua triet
tai hoi » tai khoi, dai hoi, tai hai
ky dang » ky nang, ky danh
ky hang » ky nang, ly hang, ty hang
te sac » te sach, te cac, te san

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

• If you are trying to use Boolean operators, they must be ALL CAPS: te sac ((ky hang) OR (ky dang)) tai hoi. hieu vien cac ((duc van) OR (hoc can)) hanh vai cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sac ((ky hang) OR (ky dang)) tai hoi. hieu vien cac ((duc van) or (hoc can)) hanh vai cua tre~".
• Adding a wildcard symbol may retrieve word variants: te sac ((ky hang) OR (ky dang)) tai hoi. hieu vien cac ((duc van) or (hoc can)) hanh vai cua tre*.