The Two-Piece Normal, Binormal, or Double Gaussian Distribution: Its   Origin and Rediscoveries
  This paper traces the history of the two-piece normal distribution from its origin in the posthumous Kollektivmasslehre (1897) of Gustav Theodor Fechner to its rediscoveries and generalisations. The denial of Fechner's originality by Karl Pearson, reiterated a century later by Oscar Sheynin, is shown to be without foundation. 
Kenneth F. Wallis
stat.ME