reserve i, j, m, n for Nat,
  z, B0 for set,
  f, x0 for real-valued FinSequence;

theorem Th10:
  {} is Permutation of {}
proof
A1: rng {}={};
  dom {}={};
  then reconsider f={} as Function of {},{} by A1,FUNCT_2:1;
  f is one-to-one onto Function of {},{} by A1,FUNCT_2:def 3;
  hence thesis;
end;
