Columbia subject headings:
Harvard subject headings:
Abū Bakr, Caliph, -634
Caliphate--History.
Caliphs--Biography
Islamic Empire--History--622-661.
ʻAlī ibn Abī Ṭālib, Caliph, approximately 600-661
ʻUmar ibn al-Khaṭṭāb, Caliph, -644
ʻUthmān ibn ʻAffān, Caliph, -656
Princeton subject headings:
Abū Bakr, Caliph, -634.
Caliphate--History.
Caliphs--Biography.
Islamic Empire--History--622-661.
ʻAlī ibn Abī Ṭālib, Caliph, approximately 600-661.
ʻUmar ibn al-Khaṭṭāb, Caliph, -644.
ʻUthmān ibn ʻAffān, Caliph, -656.