reserve
  a for natural Number,
  k,l,m,n,k1,b,c,i for Nat,
  x,y,z,y1,y2 for object,
  X,Y for set,
  f,g for Function;
reserve p,q,r,s,t for FinSequence;
reserve D for set;
reserve a, b, c, d, e, f for object;

theorem
  for a being object holds canFS({a}) = <* a *>
proof
  let a be object;
A1: rng canFS({a}) = {a} by FUNCT_2:def 3;
  len canFS({a}) = card {a} by Th92
    .= 1 by CARD_1:30;
  hence thesis by A1,Th39;
end;
