Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
cua tre » cua te, cuu tre, cua triet
va tinh » may tinh
cao duc » dao duc, cao suc, giao duc
van cao » van dao, van bao, van hao
tang ho » tang cho, tang ha, tang o
tung ho » tuong ho, trung hoc, trung hoa
sac ky » cac ky, sai ky
tu sac » tu sach, tu cac, tu san

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sac ky ((tang ho) OR (tung ho)) hoi. hieu van cao duc ((van hanh) or (va tinh)) dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky ((tang ho) OR (tung ho)) hoi. hieu van cao duc ((van hanh) OR (va tinh)) dai cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sac ky ((tang ho) OR (tung ho)) hoi. hieu van cao duc ((van hanh) or (va tinh)) dai cua tre*".