Note 15 — Introductory material

See “Omar Khayyám and his position in the History of Sufism,” to be found at end of the singularly attractive volume entitled “Sufi Interpretations ...” by C. H. A. Bjerregaard, New York, 1902. For an account of Omar Khayyám—Kheyyám (died in 1123), who was a very distinguished Persian philosopher, mathematician, poet and astronomer, also Director of the Bagdad Observatory, consult the ninth ed. of the “Encycl. Britann.,” Vol. XVII. pp. 771–772; “La Grande Encycl.,” Vol. XXV. pp. 372–373; “The Universal Cyclopædia,” Chas. Kendall Adams, New York, 1900, Vol. VIII. p. 588.