John Buridan
http://plato.stanford.edu/entries/buridan/
http://www.fordham.edu/gsas/phil/klima/Intro.htm
http://www.fordham.edu/gsas/phil/klima/BuridanSubstantialConcepts.htm
http://www.quantonics.com/Hughes_on_Buridan_Review.html
http://www.humanities.mq.edu.au/Ockham/wburlat.html
http://yalepress.yale.edu/yupbooks/pdf/0300084250.pdf
http://www.nd.edu/~afreddos/papers/buridan.htm
http://www.clas.ufl.edu/users/rhatch/HIS-SCI-STUDY-GUIDE/0039_jeanBuridan.html