Perhaps you should try some spelling variations:
thanh hai » thanh phan, thanh hoa, thanh san
hang hai » hoang hai, hang tai, hang va
cua tre » cua te, cuu tre, cua triet
cam duc » cam xuc, cao duc, pham duc
hieu va » lieu va, hieu qua
bai ky » ban ky, bac ky, dai ky
nang o » nang co, nang ho, nang ro
sai ky » sac ky
va cam » va cham, va cac, va cao
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: tu ((bai ky) or (sai ky)) nang o hoi. hieu va cam duc va ((hang hai) OR (thanh hai)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((bai ky) OR (sai ky)) nang o hoi. hieu va cam duc va ((hang hai) OR (thanh hai)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((bai ky) or (sai ky)) nang o hoi. hieu va cam duc va ((hang hai) OR (thanh hai)) cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((bai ky) or (sai ky)) nang o hoi. hieu va cam duc va ((hang hai) OR (thanh hai)) cua tre*.