reserve A for Tolerance_Space,
  X, Y for Subset of A;

theorem Th12:
  LAp X c= X
proof
  let x be object;
  assume x in LAp X;
  then consider y being Element of A such that
A1: y = x & Class (the InternalRel of A, y) c= X;
  y in Class (the InternalRel of A, y) by EQREL_1:20;
  hence thesis by A1;
end;
