1 Pediatric Unit, Dept of Mother and Child Health, Salesi Children's Hospital, Ancona, Italy.
2 Dept of Diseases of the Thorax, Ospedale GB Morgagni, Forlì, Italy; Dept of Respiratory Diseases & Allergy, Aarhus University Hospital, Aarhus, Denmark.
3 Pediatric Unit, Dept of Mother and Child Health, Salesi Children's Hospital, Ancona, Italy. Electronic address: [email protected].