Columbia subject headings:
ʻUmar ibn al-Khaṭṭāb, Caliph, d. 644--Biography--Early works to 1800.
Harvard subject headings:
Caliphs--Biography.
ʻUmar ibn al-Khaṭṭāb, Caliph, -644.
Princeton subject headings:
ʻUmar ibn al-Khaṭṭāb, Caliph, -644--Biography--Early works to 1800.