reserve X for non empty TopSpace;
reserve X for non empty TopSpace;
reserve X for non empty TopSpace,
  X0 for non empty maximal_Kolmogorov_subspace of X;

theorem
  X0 is_a_retract_of X
proof
  ex r being continuous Function of X,X0 st r is being_a_retraction by Th22;
  hence thesis by BORSUK_1:def 17;
end;
