How are earthworms classified

REFERENCES

1.  www.amonline.net.au/factsheets/earthworms.htm
2.  Science Insights, Addison-Wesley, 2001
3.  Holt Life Science Textbook, Holt, Rinehart and Winston, 2001
4.  Biology- A Guide to the Natural World, David Krogh, 2005
5.  www.nysite.com/nature/fauna/erthworm.htm
6.  Carolina Tips, Using The Earthworm and Pig, Spring 2004, Volume 67, No. 1
7.  www.naturewatch.com/english/wormwatch/about/ecology.html
                                                                             
                                                                                     References for Pictures

1. www.wormpost.com/worms/anatomy_pic2.html
2. agent4.deviantart.com/journal/
3. www.anselm.edu/.../genbios/surveybi04.html
4. www.kwic.com/.../species/insects/worms.htm
5. www.recyclezone.org.uk/home_az.aspx
6. http://www.naturewatch.ca/english/wormwatch/about/ecology.html