Hello,
a revision of the genus Epithelantha was made, with description of new taxa.
Donati, D., Zanovello, C., 2010: Epithelantha F.A.C. Weber ex Britton & Rose: nuovi dati su ontogenia, fertilità, simpatria e revisione del genere. Piante Grasse 30(4): 165-187
Here's the link where you can find the original article:
http://www.atmosfera-d.it/images/stories/pdf/4_10_Epith.pdf
Best regards
Davide