Graptolite Net – Graptolite.net Klassifikasjon av Cephalodiscoidea (Graptolithoidea) – Graptolite.net – BIG G – The British & Irish Graptolite Group – British and Irish Graptolite Group (BIG-G) Graptolittforekomster – The palaeoecology and palaeoenvironment of graptolitic mudrocks Written by Josh Caplan for Professor Bill Chaisson's Invertebrate Paleontology course in December 2000.