I am the mother of my son who is 20 years old, and want to bring my son to the united state of america.My x husband has given him permission to come to usa and reside with me. I mmigration offics has asked me to have a notorize letter that states the father has no problem to see his son to join her mother in usa. Please help me me to write this letter and make it it ready for notorize.

I am the mother of my son who is 20 years old, and want to bring my son to the United State of America.My x husband has given him permission to come to usa and reside with me. The immigration office has asked me to have a notorize letter that states the father has no problem to see his son to join her mother in usa. Please help me to write this letter and make it it ready for notorize.
You all help is greqatley appreciated regarding this matter.