1. Laboratory of Respiratory BiologyNational Institute of Environmental Health SciencesNational Institutes of HealthDepartment of Health and Human ServicesResearch Triangle ParkNorth CarolinaUSA
2. Center for Clinical Epidemiology BiostatisticsUniversity of Pennsylvania School of MedicinePhiladelphiaPennsylvaniaUSA
3. Pulmonary, Allergy and Critical Care DivisionDepartment of MedicineUniversity of Pennsylvania School of MedicinePhiladelphiaPennsylvaniaUSA
4. Johns Hopkins Bloomberg School of Public HealthBaltimoreMarylandUSA
5. Children's Hospital of PhiladelphiaPhiladelphiaPennsylvaniaUSA
6. Center for TARAUniversity of TsukubaTennoudaiTsukubaJapan