E. B.  Cutler, The Sipuncula. Their systematics, biology and evolution. Ithaca, N.Y.: Cornell University Press, 1994, p. 453 pp.

E. B.  Cutler and Cutler, N. J., ?A revision of the genus Aspidosiphon (Sipuncula)?, Proceedings of the Biological Society of Washington, vol. 102, pp. 826-865, 1989.

C. M.  Yonge, ?A note on mutualism between sipunculans and Scleractinian corals?, International Symposium of Sipuncula and Echiura, vol. 1. Naucno Delo Press, Belgrade, pp. 305-311, 1975.

A. C.  Stephen and Edmonds, S. J., The phyla Sipuncula and Echiura. London: Trustees British Mus. (Nat. Hist.), 1972, p. 528 pp.

E.  Wesenberg-Lund, ?Gephyrea?, Bulletin Musee royal d?Histoire naturelle de Belgique, vol. 13, pp. 1-23, 1937.

E.  Wesenberg-Lund, ?Gephyrea?, Zoology of Iceland, vol. 2, pp. 1-16, 1937.

R. V.  Chamberlin, ?Gephyrea?, Report of the Canadian Arctic Expedition 1913-18, vol. 9, pp. 3-7, 1920.

R.  Southern, ?Gephyrea of the coasts of Ireland?, Scientific Investigations of the Fisheries Branch, Department of Agriculture for Ireland, vol. 3, pp. 1-46, 1913.