Oracle's ETRM

Have you ever wondered how Oracle applications go together sometimes?  Several times I've used their Electronic Technical Reference Manual, also known as ETRM, located here which requires a login (OTN I believe, but correct me if I'm wrong) but also has R12 included too.  I used it with one of my recent issues, just because it was easier to navigate around a few pieces of related code, and I'll be adding it to the links on the side too since this isn't the first time I've used it.