On a Contribution of Freiman to Additive Number Theory.
01 January 1990
An elementary proof is provided for a claim of G. A. Freiman which says that if 2 = lambda 4 then there is a positive constant c such that, for every finite set X of points in the plane, if every line in the plane contains fewer than c |X| points of X , then the sum set X + X contains more than lambda |X| points.