Urban air pollution and emergency admissions for asthma in four European cities: the APHEA Project.
J Sunyer, C Spix, P Quénel, A Ponce-de-León, A Pönka, T Barumandzadeh, G Touloumi, L Bacharova, B Wojtyniak, J Vonk, L Bisanti, J Schwartz, K Katsouyanni
Thorax Sep 1997, 52 (9) 760-765; DOI: 10.1136/thx.52.9.760