Perhaps you should try some spelling variations:
qua thanh » quan thanh, cua thanh, qua than
thanh vi » hanh vi, thanh va, thanh ve
trung ha » trung hoc, trung tam, trung cap
can ban » van ban, toan ban
con ban » con bang, co ban, coc ban
cua tre » cua te, cuu tre, cua triet
lang ha » long ha
vi cua » vai cua, di cua
te cac » tu cac, ve cac, te cao

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 cac ky ((lang ha) OR (trung ha)) hoi. hieu qua thanh ((con ban) OR (can ban)) thanh vi cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te cac ky ((lang ha) or (trung ha)) hoi. hieu qua thanh ((con ban) OR (can ban)) thanh vi cua tre~".
• Adding a wildcard symbol may retrieve word variants: te cac ky ((lang ha) or (trung ha)) hoi. hieu qua thanh ((con ban) OR (can ban)) thanh vi cua tre*.