Harry A. ten Hove, and Peter van den Hurk. 1993. “A Review of Recent and Fossil Serpulid ’reefs’; Actuopalaeontology and the ’Upper Malm’ Serpulid Limestones in NW Germany”. Netherlands Journal of Geosciences 72 (January):23-67. https://njgjournal.nl/index.php/njg/article/view/12498.