"Silurium": 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) (Textus apud Google Books)