An elderly Athens, Tennessee, woman succumbed to injuries today sustained in a house fire last Wednesday. Officers say 87-year-old Mamie L. Folberg and her son, 48-year-old Mark R. Folberg, were in the East Madison Avenue residence when the fire broke out. Both were flown to Vanderbilt Medical Center in Nashville for treatment of severe burns. Mark Folberg is listed in stable condition. A firefighter who was injured while battling the fire has returned to active duty.