van der Land, J. (1975). Priapulida, in: Giese, A.C. et al. (Ed.) Reproduction of marine invertebrates: 2. Entoprocts and lesser Coelomates. pp. 55-65
In: Giese, A.C.; Pearse, J.S. (Ed.) (1975). Reproduction of marine invertebrates: II. Entoprocts and lesser Coelomates. Academic Press: New York. ISBN 0-12-282502-0. XIII, 344 pp. https://dx.doi.org/10.1016/B978-0-12-282502-6.X5001-8, more
