Here is a nice 40 minute breakdown of the Irish Collar from Neil Melanson head instructor of Extreme Couture. This works well into my Entangled Arm (overhook guard) game and it has given me some good ideas about using your legs and working your guard!
I am curious to see what Neil's book "Mastering Triangle Chokes" has to offer. The only other text solely devoted to Triangles is by Rigan Machado and David Meyer and is one of the best books on Jits ever written. Unfortunately it is out of print and copies on EBay are often in the $150-200 range! So I am curious to check Neil's text out when it is released.