theorem
  t is not compound implies ex s,x st t = x-term
  proof reconsider d = t as Term of S,X by MSAFREE4:42;
    assume t.{} nin [:the carrier' of S, {the carrier of S}:];
    then consider s,x such that
A1: d.{} = [x,s] by MSATERM:2;
    take s,x;
    thus thesis by A1,MSATERM:5;
  end;
