@techreport{Centers for Disease Control and Prevention (CDC)2017,
author = {Centers for Disease Control and Prevention (CDC)},
title= {NCHS urban-rural classification scheme for counties},
year = {2017},
URL = {https://www.cdc.gov/nchs/data_access/urban_rural.htm},
publisher = {National Center for Health Statistics},
address = {Hyattsville},
}