
theorem Th57:
  for L being RelStr, S1,S2 being full SubRelStr of L st the
  carrier of S1 = the carrier of S2 holds the RelStr of S1 = the RelStr of S2
proof
  let L be RelStr, S1,S2 be full SubRelStr of L;
  the InternalRel of S1 = (the InternalRel of L)|_2 the carrier of S1 by Def14;
  hence thesis by Def14;
end;
