Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
so sach » so sanh, bo sach, co sach
hieu su » hieu sau, tieu su, hieu so
tai cua » thai cua, tai cuc, tri cua
kham oc » kham cuoc
cua tre » cua te, cuu tre, cua triet
sach ty » sach y, sach tu, sach thu
hieu vu » hieu va, hieu ve, dieu vu
lang ha » long ha
oc van » hoc van, luoc van, quoc van

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ty ((nang cao) or (lang ha)) hoi. ((hieu vu) OR (hieu su)) kham oc van hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ty ((nang cao) OR (lang ha)) hoi. ((hieu vu) OR (hieu su)) kham oc van hanh tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ty ((nang cao) or (lang ha)) hoi. ((hieu vu) OR (hieu su)) kham oc van hanh tai cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ty ((nang cao) or (lang ha)) hoi. ((hieu vu) OR (hieu su)) kham oc van hanh tai cua tre*.