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2. US Department of Health and Human Services. Step it up! The Surgeon General's call to action to promote walking and walkable communities. Washington, DC: US Department of Health and Human Services, Office of the Surgeon General; 2015. https://www.hhs.gov/sites/default/files/call-to-action-walking-and-walkable-communites.pdf
3. US Department of Health and Human Services. Physical activity guidelines for Americans, 2nd edition. Washington, DC: US Department of Health and Human Services; 2018. https://health.gov/paguidelines/second-edition/pdf/Physical_Activity_Guidelines_2nd_edition.pdf
4. Community Preventive Services Task Force. Physical activity. Atlanta, GA: Community Preventive Services Task Force; 2018. https://www.thecommunityguide.org/topic/physical-activity
5. Ratcliffe M, Burd C, Holder K, Fields A. Defining rural at the U.S. Census Bureau. Washington, DC: US Department of Commerce; 2016. https://www.census.gov/content/dam/Census/library/publications/2016/acs/acsgeo-1.pdf