Columbia subject headings:
Daʻwah (Islam)
Islamic Empire--History.
ʻUmar ibn al-Khaṭṭāb, Caliph, -644.
Harvard subject headings:
Daʻwah (Islam)--History.
Islam--History
Islamic Empire--History--622-661.
Princeton subject headings:
Daʻwah (Islam)--History.
Islam--History.
Islamic Empire--History--622-661.
ʻUmar ibn al-Khaṭṭāb, Caliph, -644.