 reserve T for Ternary_Boolean_Algebra;
 reserve a,b,c,d,e for Element of T;
 reserve x,y,z for Element of T;

theorem
  Tern (b`,b,a) = Tern (a,b,b`)
  proof
    Tern (b`,b,a) = a by TLADef;
    hence thesis by TRADef;
  end;
