What are the citizenships that are shared by singers with a birth year before 1945 and after 1955?
SELECT Citizenship FROM singer WHERE Birth_Year  <  1945 INTERSECT SELECT Citizenship FROM singer WHERE Birth_Year  >  1955
SELECT Citizenship FROM singer WHERE Birth_Year  <  1945 INTERSECT SELECT Citizenship FROM singer WHERE Birth_Year  >  1955
[{'Citizenship': 'United States'}]