In 2012, I did a presentation at SHARE in Atlanta on the details of the dual-address-space (DAS) and linkage-stack (LS) architecture which includes BAKR and PR. Most likely, this contains far more detail than any sane person would want to know, but it's easier to digest than the description in the PoO.
The Assembler List section of the UGA list server doesn't support attachments or I would have posted it here. If you would like a copy, please contact me via email, and I'll forward you a PowerPoint file. (Please don't repost your request here.)
