Thomsen, Erik. “Lower Cretaceous Calcareous Nannofossil Biostratigraphy in the Danish Central Trough”. Danmarks Geologiske Undersøgelse Serie A 20 (December 30, 1987): 1–89. Accessed May 4, 2024. https://geusjournals.org/index.php/seriea/article/view/7039.