↑(en) J.M. Adrian, Early Palaeozoic Biogeography and Palaeogeography, vol.38, Geological Society of London, coll.«Memoirs of the Geological Society of London», , 490p. (ISBN978-1-86239-373-8 et 1-86239-373-7, lire en ligne), «20. A synopsis of Ordovician trilobite distribution and diversity»