@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} } @article {3783, title = {Critique of "Precipitation in Light Extinction Reconstruction" by P.A. Ryan}, journal = {Journal of the Air \& Waste Management Association}, volume = {56}, year = {2006}, month = {May}, pages = {539-546}, keywords = {Acid rain, Air particles, Visibility}, url = {http://www.environmental-expert.com/Files\%5C6477\%5Carticles\%5C6608\%5Cschichtel.pdf}, author = {Schichtel, Bret A and Malm, William C and Pitchford, Marc L} }