"Professor Sedgwick then described in descending order the groups of slate rocks, as they are seen in Wales and Cumberland. To the highest he gave the name of Upper Cambrian group. ... To the next inferior group he gave the name of Middle Cambrian. ... The Lower Cambrian group occupies the S.W. coast of Cærnarvonshire" (p. 60) in A. Sedgwick, R. I. Murchison, "On the Silurian and Cambrian systems, exhibiting the order in which the older sedimentary strata succeed each other in England and Wales" sub "Notices and Abstracts of Communications to the British Association for the Advancement of Science at the Dublin meeting, August 1835" pp. 59-61, in Report of the Fifth Meeting of the British Association for the Advancement of Science, held at Dublin in 1835 (1836)
"Cambrium": Robertus Koeppel, Praelectiones geologiae et praehistoriae pars 1 iii (Romae, 1933) p. 5 (Paginae selectae apud Google Books)
De historia nominis definitionisque vide: Mary Grace Wilmarth, The Geologic Time Classification of the United States Geological Survey Compared With Other Classifications, accompanied by the original definitions of era, period and epoch terms (United States Geological Survey Bulletin no. 769. Vasingtoniae: U.S. Government Printing Office, 1925) (p. 92 apud Google Books)
