[أحمد سعد الدين]

http://www.cimt.plymouth.ac.uk/proje...ry/default.htm

http://www.cimt.plymouth.ac.uk/proje...ook7/book7.htm

http://www.math.ucsd.edu/~ebender/CombText/index.html

http://www.gnarlymath.com/gnarbook.html