Etiquette in Addressing Doctors

When both halves of a couple are medical doctors, the envelope can be addressed as
follows:
The Doctors Peterson
or
Doctor (Dr.) Judith Peterson
and Doctor (Dr.) Michael Peterson
or
Doctors Judith and Michael Peterson
If Judith goes by her maiden name, the correct form is
Dr. Judith Holmes and Dr. Michael Peterson
If only the husband is a doctor:
Dr. and Mrs. Michael Peterson
or
Dr. Michael Peterson and Ms. Judith Holmes
The name with the title goes first. So, if Judith is the doctor:
Dr. Judith Holmes and Mr. Michael Peterson