Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
hanh hai » thanh hai, nhanh hai, hang hai
sang xa » song xa, lang xa, sang ma
nang ma » tang ma, sang ma, nang cao
qua cac » cua cac
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
hai cua » thai cua, dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet
tu sai » tu bai, tu san, tu cai
sai ky » sac 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 sai ky ((sang xa) or (nang ma)) hoi. hieu qua cac duc van hanh hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sai ky ((sang xa) OR (nang ma)) hoi. hieu qua cac duc van hanh hai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sai ky ((sang xa) or (nang ma)) hoi. hieu qua cac duc van hanh hai cua tre*.