Kuehni Claudia E, Brooke Adrian M, Strippoli Marie-Pierre F, Spycher Ben D, Davis Anthony, Silverman Michael
Swiss Paediatric Respiratory Research Group, Department of Social and Preventive Medicine, University of Berne, Berne, CH-3012, Switzerland.
Int J Epidemiol. 2007 Oct;36(5):977-85. doi: 10.1093/ije/dym090. Epub 2007 Oct 2.