Perhaps you should try some spelling variations:
cam thuc » am thuc, nam thuc, can thuc
van hanh » van thanh, ban hanh, van anh
hanh hai » thanh hai, nhanh hai, hang hai
nang xa » lang xa, nang ma, mang xa
hieu ve » hieu va, hieu van
cam thu » nam thu, cac thu, ca thu
hai cua » thai cua, dai cua, hoi cua
cua tre » cua te, cuu tre, cua triet

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu cac ky ((nang xa) or (nang x)) hoi. hieu ve ((cam thuc) or (cam thu)) van hanh hai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu cac ky ((nang xa) OR (nang x)) hoi. hieu ve ((cam thuc) OR (cam thu)) van hanh hai cua tre.
• Adding a wildcard symbol may retrieve word variants: tu cac ky ((nang xa) or (nang x)) hoi. hieu ve ((cam thuc) or (cam thu)) van hanh hai cua tre*.