I know my instructor has gotten a book published, I think it's called Juji Gatame: Secrets of the Cross-Body Armlock. He's a 7th dan and been doing this for a long time so check it out if you can find it.
He's Kodokan, not BJJ, but hey a juji's a juji, right?
"**** OFF! Judean People's Front...We're the PEOPLE'S FRONT OF JUDEA!" - The Life of Brian