Perhaps you should try some spelling variations:
vat hanh » vat thanh, van hanh, va hanh
sach thu » sach thue, sach thieu, sach tham
cham hoc » cham soc, chat hoc, cham hoi
hieu va » lieu va, hieu qua
hoc vat » hoc va, hoc viet, thuc vat
cua tre » cua te, cuu tre, cua triet
sach ty » sach y, sach tu, xach tay
dieu vu » dien vu, dieu va, dieu cua
xang xa » lang xa, mang xa, ang 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: tu ((sach ty) or (sach thu)) xang xa hoi. ((dieu vu) or (hieu va)) cham hoc vat hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ty) OR (sach thu)) xang xa hoi. ((dieu vu) OR (hieu va)) cham hoc vat hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu ((sach ty) or (sach thu)) xang xa hoi. ((dieu vu) or (hieu va)) cham hoc vat hanh vi cua tre*.