J.M.J. Vergoossen. 1992. “On Complex Dermal Elements in Loganellia Species (Agnatha, Thelodonti) from the Upper Llandovery of Scotland (l.G.C.P. 328 Contribution)”. Netherlands Journal of Geosciences 71 (January):51-64. https://njgjournal.nl/index.php/njg/article/view/12530.