1. Anctil, M., J.-P. De Waele & A. K. Pani, 1990. Monoamines in the nervous system of the tube-worm Chaetopterus variopedatus (Polychaeta): Biochemical detection and serotonin immunoreactivity. Cell. Tiss. Res. 259: 81–92.
2. Anlauf, A., 1989. Die Charakterisierung von Populationen des Schlammröhrenwurms Tubifex tubifex (Müller) mit Hilfe von enzymelektrophoretischen, populationsgenetischen und ökologischen Methoden. Doctorate thesis, Universität Köln: 127 pp.
3. Barlow, L. A. & J. W. Truman, 1991. Patterns of serotonin and SCP immunoreactivity during metamorphosis of the nervous system of the red abalone, Haliotis rufescens. J. Neurobiol. 23: 829–844.
4. Bullock, T. H. & G. A. Horridge, 1965. Structure and function in the nervous systems of invertebrates. Vol. 1. W. H. Freeman and Company, San Francisco. 798 pp.
5. Clark, R. B., 1964. Dynamics in metazoan evolution. The origin of the coelom and segments. Clarendon Press, Oxford: 313 pp.