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
vai cua » dai cua, hai cua, lai cua
sach ty » sach y, sach tu, sach thu
su sach » so sach, vu sach
mang xa » lang xa, mang may, dang xay
cua tre » cua te, cuu tre, cua triet
xac va » tac va, ac va, bac va
tuc va » thuc va, truc va, tuc xa
ang xa » lang xa, dang xay, hoang xa

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ty ((ang xa) OR (mang xa)) hoi. hieu vien cac ((xac va) or (tuc va)) hanh vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty ((ang xa) OR (mang xa)) hoi. hieu vien cac ((xac va) OR (tuc va)) hanh vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ty ((ang xa) OR (mang xa)) hoi. hieu vien cac ((xac va) or (tuc va)) hanh vai cua tre".
• Adding a wildcard symbol may retrieve word variants: su sach ty ((ang xa) OR (mang xa)) hoi. hieu vien cac ((xac va) or (tuc va)) hanh vai cua tre*.