@article {11561, title = {Widespread Reductions in Haze across the United States from the Early 1990s through 2011}, journal = {Atmospheric Environment}, volume = {94}, year = {2014}, month = {May 27}, pages = {671-679}, publisher = {Elsevier}, keywords = {Air pollution, Air quality}, author = {Hand, Jennifer L and Schichtel, Bret A and Malm, William C and Copeland, S. and Molenar, J. V and Frank, N. and Pitchford, Marc L} }