reserve T for non empty TopSpace,
  A, B for Subset of T,
  F, G for Subset-Family of T;

theorem Th35:
  [#]T is F_sigma
proof
  reconsider F = { [#]T } as Subset-Family of T;
  F is closed & [#]T = union F by Th20,ZFMISC_1:25;
  hence thesis;
end;
