Wow Howard, it sounds as though you have your work cut out for you. Who was the informant for the information on the death certificate? If it was the doctor or a hospital appointee, then your mother probably gave the information on the day she was admitted. But if it was someone else (a relative maybe), is that person still living?

Have you ever tried to get a birth certificate on your mother? As her son, you would be able to do this. You have the important info (date and place of birth).