Coal mines and mining. Employment and related statistics of mines and quarries, 1935: pt. 1, Bituminous coal, by F. G. Tryon, W. H. Young, M. E. Wilson, and F. E. Berquist; pt. 2, Pennsylvania anthracite, by F. G. Tryon, M. Otero, W. H. Young, and D. C. Ashmead.