The description of the constructors for the ZipfDistribution class specifies an argument of type doule, called exponent. The documentation refers to a MathWorld page where the distribution is defined. However, here the exponent p, is the exponent of the cdf, not of the pdf (which is then p + 1). After running some test I found that the exponent in the constructor is the one for the pdf. This can create confusion among users. Therefore I recommend specifying in the documentation which exponent is meant.