http://en.wikipedia.org/wiki/Gottfried_Leibniz
http://www.radicalacademy.com/philleibniz.htm
_ Anthony Quinton on Spinoza and Leibniz: Section 1
http://www.youtube.com/watch?v=GmbGbo-oyKc
_ Gottfried Leibniz
http://www.youtube.com/watch?v=NzqgCm4MEtw
_ Leibniz calculus notation explained for derivatives
http://www.youtube.com/watch?v=qYA2bDcZH18
_ Leibniz quest for Pi pt1
http://www.youtube.com/watch?v=GAkkTa2XpEc