Geology of East Somerset and the Bristol coal-fields : or, Descriptions of the rocks comprised in sheet 19, part of sheet 35, and adjoining portions of sheets 18, 20, and 21, of the (one inch) Geological survey map of England - Woodward, Horace B. (Horace Bolingbroke), 1848-1914 (Memoirs of the Geological Survey of Great Britain. England and Wales., 1876)