on which has the least error. Definition The probability mass function is given, as a function of the rank n, by where b and c are parameters of the distribution. See also Zipf's law References Laherrère J, Deheuvels P (1996) "Distributions de type 'fractal parabolique' dans la nature" (French, with English summary: "Parabolic fractal" distributions in nature), (http://www.hubbertpeak.com/laherrere/fractal.htm) Comptes rendus de l'Académie des sciences, Série II a: Sciences de la Terre et des Planétes, 322, (7), 535–541 Discrete distributions