Dear Linda,
Haven't seen you for ages.I miss you very much.
I hate to bother you but there is something I need your assistance.In application for the VISA to the U.S.,a residence address and an invitation letter from that address are needed.We filled in the application form with your address and therefore,would have to ask for your help to issue an invitation letter to my son.
We thank you very much for your help in advance.
Yours Sincerely,
xxx