Perhaps you should try some spelling variations:
quoc tuan » quoc quan, quoc toan, quoc quang
hieu van » hieu va, thien van, lieu va
hau quoc » han quoc, ha quoc, phan quoc
anh thai » anh thi, anh tai, nhanh thai
thai cua » than cua, tai cuc, tri cua
van hau » van ha, van hai, van dau
cua tre » cua te, cuu tre, cua triet
sac ky » cac ky, sai ky
nang o » nang co, nang ho, nang ro
o hoc » co hoc, mo hoc, so hoc

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 y) or (sac ky)) nang o hoc. hieu van hau quoc tuan anh thai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach y) OR (sac ky)) nang o hoc. hieu van hau quoc tuan anh thai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu ((sach y) or (sac ky)) nang o hoc. hieu van hau quoc tuan anh thai cua tre*.