^Rossignol, Rosalyn (2006). Critical Companion to Chaucer: A literary Reference to His Life and Work. New York, NY: Facts on File. p. 612. ISBN 0816061939.
^Ibn Khaldun (1989). The Muqaddimah: An Introduction to History. Princeton, NJ: Princeton University Press. p. Back Cover. ISBN 0691017549.
^Grant, Edward (2002). "Nicole Oresme". In Curren, Randall. A Companion to the Philosophy of Education. Blackwell Publishing. ISBN 0631216723.
^Bediuzzaman Said Nursi (2008). The Reasonings: A Key to Understanding the Qu'ran's Eloquence. Somerset, NJ: Tughra Books. p. 50. ISBN 9781597841290.