theorem
  Firing(t, M0) = Firing(<*t*>, M0)
  proof
    set Q = <*t*>;
    consider M be FinSequence of nat_marks_of PTN such that
A1: len Q = len M & Firing(Q, M0) = M/.len M & M/.1 = Firing(Q/.1, M0) &
    for i st i < len Q & i > 0 holds M/.(i+1) = Firing(Q/.(i+1),M/.i) by Defb;
    thus Firing(<*t*>, M0) = Firing(<*t*>/.1, M0) by A1,FINSEQ_1:39
    .= Firing(t, M0) by FINSEQ_4:16;
 end;
