Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
so tang » son tang, so trang, do tang
cao duc » dao duc, cao suc, giao duc
vai cua » dai cua, hai cua, lai cua
va hanh » va thanh, va danh, ban hanh
cua tre » cua te, cuu tre, cua triet
tang ky » dang ky, trong ky, tang khu
cac duc » cac du, cac dac, cac nuoc
hieu ve » hieu va, hieu van
lang xa » lang ha, dang xay, lang van
ky lang » ky nang, ky dang, ky tang

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

• Performing a fuzzy search may retrieve terms with similar spellings: so tang ky lang xa hoi. hieu ve ((cac duc) or (cao duc)) ((va hanh) OR (van hanh)) vai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so tang ky lang xa hoi. hieu ve ((cac duc) OR (cao duc)) ((va hanh) OR (van hanh)) vai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so tang ky lang xa hoi. hieu ve ((cac duc) or (cao duc)) ((va hanh) OR (van hanh)) vai cua tre".
• Adding a wildcard symbol may retrieve word variants: so tang ky lang xa hoi. hieu ve ((cac duc) or (cao duc)) ((va hanh) OR (van hanh)) vai cua tre*.