Perhaps you should try some spelling variations:
cac thuc » cach thuc, can thuc, cay thuc
day danh » day manh, dai danh, dao danh
danh dai » danh dau, danh di, danh sai
nang xa » lang xa, nang ma, mang xa
hieu ve » hieu va, hieu van
cac thu » cach thuc, cac thoi
cua tre » cua te, cuu tre, cua triet
sinh y » sinh ly

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

• Performing a fuzzy search may retrieve terms with similar spellings: hoc sinh y ((nang xa) or (nang x)) hoi. hieu ve ((cac thuc) OR (cac thu)) day danh dai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: hoc sinh y ((nang xa) OR (nang x)) hoi. hieu ve ((cac thuc) OR (cac thu)) day danh dai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc sinh y ((nang xa) or (nang x)) hoi. hieu ve ((cac thuc) OR (cac thu)) day danh dai cua tre".
• Adding a wildcard symbol may retrieve word variants: hoc sinh y ((nang xa) or (nang x)) hoi. hieu ve ((cac thuc) OR (cac thu)) day danh dai cua tre*.