http://www-personal.umd.umich.edu/~dstasik/Philosophy/Knowledge/Descartes/Descartes2/index.htm

http://www-personal.umd.umich.edu/~dstasik/Philosophy/Knowledge/Descartes/Empiricus/index.htm

http://www-personal.umd.umich.edu/~dstasik/Philosophy/Knowledge/Descartes/Descartes