Snowmobile activities in the National Park System and miscellaneous national heritage bills : hearing and workshop before the Subcommittee on National Parks, Historic Preservation, and Recreation of the Committee on Energy and Natural Resources, United States Senate, One Hundred Sixth Congress, second session on the potential ban on snowmobiles in Yellowstone and Grand Teton National Parks and the recent decision by the Department of the Interior to prohibit snowmobile activities in other units of the National Park System and miscellaneous national heritage bills, May 25, 2000, May 18, 2000