Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
hanh thai » nhanh thai, hinh thai, anh thai
vien cac » vien bach, vien dai, vien da
hanh tai » thanh tai, hang tai, han tai
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach ty, sach kem
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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 ((sach ky) OR (sach y)) nang o hoi. hieu vien cac duc van ((hanh thai) OR (hanh tai)) cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach ky) or (sach y)) nang o hoi. hieu vien cac duc van ((hanh thai) OR (hanh tai)) cua tre~".
• Adding a wildcard symbol may retrieve word variants: te ((sach ky) or (sach y)) nang o hoi. hieu vien cac duc van ((hanh thai) OR (hanh tai)) cua tre*.