1. Abbot NJ (1995) Morphology of nonmamalian glia cells: functional implications. In: Kettenmann H, Ransom BR (eds) Neuroglia. Oxford University Press Inc, New York, pp 97–119
2. Ahlrichs W (1995) Ultrastruktur und Phylogenie von Seison nebaliae (Grube 1859) und Seison annulatus (Claus 1876). Hypothesen zu phylogenetischen Verwandtschafts-verhältnissen innerhalb der Bilateria. Cuvillier Verlag, Göttingen
3. Ax P (2001) Multicellular animals III. Order in nature—system made by Man. Springer, Berlin
4. Bullock TH, Horridge GA (1965) Structure and Function in the nervous system of invertebrates, vol 2. Freeman, San Francisco
5. Chase DL, Koelle MR (2007). Biogenic amine neurotransmitters in C. elegans. In WormBook, pp 1–15