The basic concept of the full profile refinement of the pair distribution function (PDF) was adapted from the program RESPAR written by Simon Billinge. The routines for the processing of the command language and the FORTRAN style interpreter are taken from the program package DISCUS by Reinhard Neder and Thomas Proffen. PDFFIT is distributed as part of that package as well as a stand-alone program. The random number generators were taken from the Numerical Recipes by Press, Flannery, Teukolsky & Vetterling, Cambridge University Press, 1989. The routines for the line editing were taken from the program GNUPLOT.