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

theorem Th36:
  [#]T is G_delta
proof
  reconsider F = { [#]T } as Subset-Family of T;
  F is open & [#]T = meet F by Th19,SETFAM_1:10;
  hence thesis;
end;
