Annals of Allergy, Asthma, and Immunology 80:189-194.
Annals of Allergy, Asthma, and Immunology 80:189-194 has information about pollen counts for every city in North America. 
mnli hypothesis: Annals of Allergy, Asthma, and Immunology 80:189-194 has information about pollen counts for every city in North America.  premise: Annals of Allergy, Asthma, and Immunology 80:189-194.