RT Journal Article SR Electronic T1 On some questions concerning the coal formations of North America JF American Journal of Science JO Am J Sci FD American Journal of Science SP 63 OP 74 DO 10.2475/ajs.s2-30.88.63 VO s2-30 IS 88 A1 Lesquereux, Leo YR 1860 UL http://www.ajsonline.org/content/s2-30/88/63.abstract AB