1. Listing of acreage report dataset;National Park Service,2015
2. Apostle Islands National Lakeshore;annual park recreation visitation and yearly public use. National Park Service,2016
3. National Park service summary report;annual park recreation visitation and yearly public use. National Park Service,2016
4. Outdoor recreation trends and futures: a technical document supporting the Forest Service 2010 RPA assessment;Cordell,2012
5. Injuries sustained at Yellowstone National Park requiring emergency medical system activation;Johnson;Wilderness Environ Med,2007