Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
hanh thai » nhanh thai, hinh thai, hanh tai
thai cua » than cua, tai cuc, tri cua
van hanh » van thanh, ban hanh, van anh
vien cac » vien bach, vien dai, vien da
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach ty, sach kem
nang ho » nang hoc, nang co, tang ho
nang o » nang co, nang ro, nang x
du van » duy van, duc van, tu van

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

• Performing a fuzzy search may retrieve terms with similar spellings: te ((sach ky) or (sach y)) ((nang o) OR (nang ho)) hoi. hieu vien cac du van hanh thai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sach ky) OR (sach y)) ((nang o) OR (nang ho)) hoi. hieu vien cac du van hanh thai cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te ((sach ky) or (sach y)) ((nang o) OR (nang ho)) hoi. hieu vien cac du van hanh thai cua tre*".