↑Smith, A. (2007). "Echinoderms: Attachment, torsion and the origins of a radical new body plan". In Budd, G.E.; Streng, M.; Daley, A.C.; Willman, S. Programme with Abstracts. Palaeontological Association Annual Meeting 51. Uppsala, Sweden.
↑Smith, A.B. (2005). «The pre-radial history of echinoderms». Geological Journal. 40 (3): 255–280. doi:10.1002/gj.1018