Honsberger (1973). "A Problem in Combinatorics". Mathematical Gems. Mathematical Association of America. Ch. 9, pp. 99–107. ISBN0-88385-301-9. Freeman, J. W. (1976). "The Number of Regions Determined by a Convex Polygon". Mathematics Magazine. 49 (1): 23–25. JSTOR2689875.
Honsberger (1973). "A Problem in Combinatorics". Mathematical Gems. Mathematical Association of America. Ch. 9, pp. 99–107. ISBN0-88385-301-9. Freeman, J. W. (1976). "The Number of Regions Determined by a Convex Polygon". Mathematics Magazine. 49 (1): 23–25. JSTOR2689875.
mit.edu
math.mit.edu
Poonen, Bjorn; Rubinstein, Michael. "The number of intersection points made by the diagonals of a regular polygon". SIAM J. Discrete Math. 11 (1998), no. 1, 135–156; link to a version on Poonen's website