1. Lower Cambrian trace fossil evidence for predation on trilobites;Alpert;Lethaia,1975
2. High-resolution biostratigraphy (conodonts and graptolites) of the Upper Ordovician and Lower Silurian - a chronometric framework in which to evaluate the causes of the mass extinction;Armstrong;Modern Geology,1995
3. Bassler R. S. 1950. Faunal Lists and Descriptions of Paleozoic Corals. Geological Society of America, Memoir, 44.
4. Bengtson S. Conway Morris S. 1992. Early radiation of biomineralizing phyla. In: Lipps J. H. Signor P. W. , (eds) q.v., 447–481.
5. Berkowski B. 1995. Calyxocorallia, their relationship to Heterocorallia and to Rugosa. VII International Symposium on fossil Cnidaria and Porifera, Madrid, September 1995, Abstracts, 6.