reserve a,a1,a2,b,c,d for Ordinal,
  n,m,k for Nat,
  x,y,z,t,X,Y,Z for set;
reserve f,g for Function;
reserve A,B,C for array;

theorem Th38:
  A is permutation of A
  proof
    take id dom A; thus thesis by RELAT_1:51;
  end;
