  Known properties of Chebyshev polynomials are the following: they have simple
critical points with only two (finite) critical values. Those properties
uniquely determine the named polynomials modulo affine transformations of
dependent and independent variables. A similar property of Zolotarev fractions:
simple critical points and only four critical values generates already many
classes of rational functions modulo projective transformations of their
dependent and independent variables. They are listed in this note.
