Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
ban hanh » ban hang
hieu va » lieu va, hieu qua
tai cua » thai cua, tai cuc, tri cua
xuc ban » duc ban, cuc ban, quoc ban
cac xuc » cam xuc, cac nuoc, chat xuc
cua tre » cua te, cuu tre, cua triet
sach ky » sach y, sach ty, sach kem
hieu ve » hieu van
cao hoc » co hoc, cho hoc, chat hoc
sac ky » cac ky, sai ky

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 ky) or (sac ky)) nang cao hoc. ((hieu ve) OR (hieu va)) cac xuc ban hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) nang cao hoc. ((hieu ve) OR (hieu va)) cac xuc ban hanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) or (sac ky)) nang cao hoc. ((hieu ve) OR (hieu va)) cac xuc ban hanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sac ky)) nang cao hoc. ((hieu ve) OR (hieu va)) cac xuc ban hanh tai cua tre*.