Reference

- Miller, Kenneth R. and Joseph Levine. Biology. 4th ed. Upper Sadle River, NJ: Prentice Hall, 1998.
- "Biology at Iowa university" 2006 http://www.biology.iastate.edu/Courses/201L/Annelida/%20AnnelINDX.htm
- "Phylum Annileda " 2004 http://www.esu.edu/~milewski/intro_biol_two/lab__12_annel_arthro/Annelida.html
- "A Hotlist of Annileda" 2006 http://www.kn.att.com/wired/fil/pages/listannelidama.html
- "Diffusion" http://www.blobs.org/science/diffusion/imgs/diffusion2.gif
- "Unsegmented Worms" http://sps.k12.ar.us/massengale/unsegmented_worm_notes_b1.htm