National Recreation Association , Weir, L. H. (Lebert Howard) , National Conference on Outdoor Recreation (U.S.) and American Institute of Park Executives. Park Recreation Areas in the United States : Bulletin of the United States Bureau of Labor Statistics, No. 462 , Washington, D.C: G.P.O., May 1928, https://fraser.stlouisfed.org/title/4051, accessed on March 10, 2025.