Can't unzip file

[Rodolfo Medina <rodolfo.medina@gmail.com>]

From

 http://www.topology.org/tex/conc/mp/

I downloaded mp1.zip and mpdemo.ps.zip,
but don't manage to unzip the second one:


$ unzip mpdemo.ps.zip
Archive:  mpdemo.ps.zip
  End-of-central-directory signature not found.  Either this file is not
  a zipfile, or it constitutes one disk of a multi-part archive.  In the
  latter case the central directory and zipfile comment will be found on
  the last disk(s) of this archive.
unzip:  cannot find zipfile directory in one of mpdemo.ps.zip or
        mpdemo.ps.zip.zip, and cannot find mpdemo.ps.zip.ZIP, period.


. The output does not tell much to me.
Anybody knows how to handle this?

Tanks,
Rodolfo