<A HREF="http://www.phystechsoft.ru/ptsdos/"
  >PTS-DOS</a> is an *(OS), a (commercial) _(DOS) clone from Russia (fast mirror in <A HREF="http://www.phystechsoft.com/ptsdos/"
  >USA</a>).
<br/>
A very old PTS DOS FAQ can be <a href="http://www.almmnet.de/ptsdos/ptsfaq.html">found here.</a>