Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
nang mai » nang ma, nang tai, lang mai
vien day » vien dai, vien da, vien xay
thuc van » thuc vat, thuc va, thuc hanh
thuc dan » thuc hanh, hoc dan, thuc vat
su sach » so sach, vu sach
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
mai hoi » mai khoi, dai hoi, lai hoi
cua tre » cua te, cuu tre, cua triet
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 nang mai hoi. hieu vien day ((thuc van) or (thuc dan)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ty nang mai hoi. hieu vien day ((thuc van) OR (thuc dan)) hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: su sach ty nang mai hoi. hieu vien day ((thuc van) or (thuc dan)) hanh vi cua tre*.