Perhaps you should try some spelling variations:
hanh hai » thanh hai, nhanh hai, hang hai
hai cua » thai cua, dai cua, hoi cua
va hanh » van hanh, va thanh, va danh
cac bao » cach bao, cac bai, cac ban
cua tre » cua te, cuu tre, cua triet
hieu va » lieu va
sac ky » sai ky
bao va » bao ve, tao va, ban va
nang o » nang co, nang ho, nang ro
o hoi » co hoi, o hoc, o hai

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

• Performing a fuzzy search may retrieve terms with similar spellings: thu ((sac ky) OR (cac ky)) nang o hoi. ((hieu va) or (hieu qua)) cac bao va hanh hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sac ky) OR (cac ky)) nang o hoi. ((hieu va) OR (hieu qua)) cac bao va hanh hai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sac ky) OR (cac ky)) nang o hoi. ((hieu va) or (hieu qua)) cac bao va hanh hai cua tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sac ky) OR (cac ky)) nang o hoi. ((hieu va) or (hieu qua)) cac bao va hanh hai cua tre*.