Entoprocts: keys and notes for the identification of the species
Nielsen, C. (1989). Entoprocts: keys and notes for the identification of the species. Synopses of the British Fauna, N.S. 41. E.J. Brill: Leiden. ISBN 90-04-08886-5. VII, 131 pp.
Part of: Barnes, R.S.K.; Crothers, J.H. (Ed.) Synopses of the British Fauna. Linnean Society of London: London; New York. ISSN 0082-1101