Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
sach thu » sach thue, sach thieu, sach tham
dang xay » dang van, van xay
vien da » vien dai, hien dai
sach ty » sach y, sach tu, xach tay
xay hoi » xa hoi, tay hoi, cay phoi
cua tre » cua te, cuu tre, cua triet
xac va » tac va, ac va, bac va
tuc va » thuc va, truc va, tuc xa
vi cua » vai cua, di cua

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) or (sach thu)) dang xay hoi. hieu vien da ((xac va) or (tuc va)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ty) OR (sach thu)) dang xay hoi. hieu vien da ((xac va) OR (tuc va)) hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: su ((sach ty) or (sach thu)) dang xay hoi. hieu vien da ((xac va) or (tuc va)) hanh vi cua tre*.