@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}
}
