Kröger, Björn. “The Lyckholm Acme of Cephalopods – Review of the Late Katian (Vormsi–Pirgu Regional Stages) Ordovician Cephalopods of Estonia”. European Journal of Taxonomy 978, no. 1 (March 3, 2025): 1–169. Accessed May 9, 2026. https://europeanjournaloftaxonomy.eu/index.php/ejt/article/view/2801.