Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hanh dai » hanh tai, hanh dao, vanh dai
van hanh » van thanh, ban hanh, van anh
duc van » duc va, duc tan, duc manh
cam duc » cam xuc, cao duc, pham duc
cua tre » cua te, cuu tre, cua triet
sach ky » sach y, sach ty, sach kem
hieu ve » hieu va
nang xa » nang x, lang xa, nang ma
sac ky » cac ky, sai ky

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

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