N:
National Coal Resources Data System - US Coal Resource Database (USGCOAL). - Searchable database for locating information on coal resources by area, coalfield, coalbed, rank, quadrangle, source, years, or characteristics of thickness, overburden, and reliability. [Department of the Interior, U.S. Geological Survey (USGS)]

P:
Premium Coal Sample Program - Provides the basic coal research community with the highest quality samples for basic research [Department of Energy (DOE), Argonne National Laboratory (ANL)]

R:
Record Group 150: Records of the National Bituminous Coal Commission, 1919 - 1936 - National Archives' Archival Research Catalog description for Record Group 150: Records of the National Bituminous Coal Commission, 1919 - 1936 [National Archives and Records Administration (NARA)]

Record Group 222: Records of the Bituminous Coal Division, 1937 - 1943 - National Archives' Archival Research Catalog description for Record Group 222: Records of the Bituminous Coal Division, 1937 - 1943 [National Archives and Records Administration (NARA)]

Record Group 223: Records of the Office of the Bituminous Coal Consumers' Counsel, 1935 - 1943 - National Archives' Archival Research Catalog description for Record Group 223: Records of the Office of the Bituminous Coal Consumers' Counsel, 1935 - 1943 [National Archives and Records Administration (NARA)]

Record Group 68: Records of the U.S. Coal Commission, 1896 - 1927 - National Archives' Archival Research Catalog description for Record Group 68: Records of the U.S. Coal Commission, 1896 - 1927 [National Archives and Records Administration (NARA)]