(1) Pippy Park 2012. Welcome to Pippy Park. Accessed from http://www.pippypark.com on March 21, 2013

(2) Bishop, G. A., Morris, J. A., & Stedman, D. H. 2001. Snowmobile Contributions to Mobile Source Emissions in Yellowstone National Park. Environmental Science and Technology, 2874-2881.



(3) Bishop, G. A., Stedman, D. H., Hektner, M., & Ray, J. D. 1999. An In-Use Snowmobile Emission Survey in Yellowstone National Park. Environmental Science and Technology, 33:3924-3926.

(4) Borkowski, J. J., White, P. J., Barrott, R. A., Davis, T., Hardy, A. R., Reinhart, D. J. 2006. Behavioural responses of bison and elk in Yellowstone to snowmobiles and snow coaches. Ecological Applications 16:1911-1925

(5) Baker, E.; Buthmann, E. 2005. Snowmobiling in the Adirondack Park: environmental and social impacts. St. Lawrence University Department of Biology. Retrieved from http://it.stlawu.edu on March 24, 2013.

(6) Liikonen L., Alanko M., Jokinen S., Niskanen I., Virrankoski jL. 2007. Snowmobile Noise. The Finnish Environment 33 en.​

(7) Arp, C. D., Simmons, T. 2012. Analyzing the impacts of off-road vehicle (ORV) trails on watershed processes in Wrangell-St. Elias National Park and Preserve, Alaska. Environmental Management 49:751-766.​

(8) Burger, J., Zappalorti, R. T., Gochfeld, M., Devito, E. 2007. Effects of off-road vehicles on reproductive success of pine snakes (Pituophus melanoleucus) in the New Jersey pinelands. Urban Ecosystems 10:275-284.

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(9) Bishop, G. A., Stadtmuller, R., Stedman, D. H., Ray, J. D. 2009. Portable emission measurements of Yellowstone Park snowcoaches and snowmobiles. Journal of the Air & Waste Management Association 59:936-942.​

(10) Shively, D. D., Pape, B. M. C., Mower, R. N., Zhou, Y., Russo, R., Sive, B. C. 2008. Blowing smoke in Yellowstone: air quality impacts of oversnow motorized recreation in the park. Environmental management 41:183-199.