↑Stephen, A. C., and. Edmonds S. J. (1972): The Phyla Sipuncula and Echiura. vii+528 Trustees of The British Museum of Natural History. London. ISBN 0-565-00717-3
↑Ditadi, A.S.F. & Migotto, A.E. (1982): O Filo Sipuncula. Concelho Nacional de Desemvolvimento Cientifico e Tecnologico CNPq Brasilia. 43p.
↑Cutler, Edward B. & Cutler, Norma J (1985): A revision of the genera Phascolion Théel and Onchnesoma Koren and Danielssen (Sipuncula). Proceedings of Biological Society of Washington 94(4):809-850
↑Cutler, Edward B. & Gibbs, Peter E. (1985): A Phylogenetic analysis of higher taxa in the Phylum Sipuncula. Systematic Zoology 34(2):162-173.
↑ Cutler, Edward B. (1994): The Sipuncula: their systematic, biology and evolution. Comstock Publishing Associates of Cornell University. Ithaca, New York. 406p ISBN 0-8014-2843-2Google Book