Library's c.2 mounted on cloth backing. "Prepared in cooperation with Division of Labor Statistics, Department of Industrial Relations, Divisions of Mine, Department of Industrial Relations, Engineering Experiment State, The Ohio State University and State Highway Testing and Research Laboratory." by G.W. White and G.C. Gambs (with the assistance of G.R. Washburn) Scale 1:500,000 ; Lambert conformal conic projection. "Base map from U.S. Geological Survey."