theorem
  Shift(stop I,n). n=Shift(I,n). n
proof
A1:  0 in dom I by AFINSQ_1:66;
  thus Shift(stop I,n). n
    =Shift(I,n).( 0 qua Nat +n) by A1,Th49
    .=Shift(I,n). n;
end;
