Nielsen, Claus: Entoprocts. Keys and notes for the identification of the species. – Synopses of the British Fauna (New Series) (Edited by Doris M. Kermack & R. S. K. Barnes) No. 41 – Leiden (E. J. Brill), 1989; 131 S., 58 meist mehrteilige Abb.; Soft cover Gld. 78, –, US $ 39. –. – ISSN 0082-1101, ISBN 9004088865