Perhaps you should try some spelling variations:
ban hanh » ban hang
mai khoi » mai khoa, tai khoa, cac khoi
ky tang » ky nang, ky dang, kho tang
sao ban » tao ban, cao bang, tao bang
va chat » van chat, va phat, cao chat
va cham » va tham
mai hoi » dai hoi, lai hoi, mai doi
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.

• If you are trying to use Boolean operators, they must be ALL CAPS: tu cac ky tang ((mai hoi) OR (mai khoi)). hieu ((va cham) OR (va chat)) sao ban hanh vi cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu cac ky tang ((mai hoi) OR (mai khoi)). hieu ((va cham) or (va chat)) sao ban hanh vi cua tre~".
• Adding a wildcard symbol may retrieve word variants: tu cac ky tang ((mai hoi) OR (mai khoi)). hieu ((va cham) or (va chat)) sao ban hanh vi cua tre*.