http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1922067/

this may help!

Dear Samreen,

I'd recommend you have a look at the following page:

http://www.cb.uu.se/~gustaf/

Hope it helps,

f.

This may sound like a very obscure publication, but it is good, still quite recent, and has excellent illustrations.  Contact Dr. Schrock at Emporia State University in Kansas; he can probably send a hard-copy.

[email protected]

Fauquest, C.M., J. R. Schrock. 2006. Classification of Viruses. Kansas School Naturalist. Vol. 53 (1): 3 - 15.