Known Specimens of SPC-SWAP, EPL, EPLX 1A-Processor Code/Documents?

[segaloco]

Since things have been quiet in my 3B/5ESS research lately, I've been reading up on 1A and 4ESS, trying to get a better feel for what came before, and fell down a rabbit hole on studying the programming environments used in that generation of switching technologies.

The three general languages used were SPC-SWAP assembly language, EPL, and EPLX, as referenced here: https://ieeexplore.ieee.org/document/810323

It seems the bulk of took place on System/360 and System/370 mainframes, most work taking place at Bell Labs Indian Hill with some remote systems in Columbus.  This is in contrast to later 3B-centric work which instead was performed largely in C on UNIX, drawing an interesting contrast between the two projects from a software development perspective.

I was wondering if anyone here has any particular knowledge of these languages or the development systems surrounding them?  I've thus far only found compelling references in these three BSTJ issues regarding TSPS (Traffic Service Position System) No. 1, 4ESS, and TSPS No. 1B respectively, as well as the above linked paper in the IEEE library:

https://bitsavers.org/magazines/Bell_System_Technical_Journal/BSTJ_V58N06_197907_Part_1.pdf
https://bitsavers.org/magazines/Bell_System_Technical_Journal/BSTJ_V60N06_198107_Part_2.pdf
https://bitsavers.org/magazines/Bell_System_Technical_Journal/BSTJ_V62N03_198303_Part_3.pdf

Given that C is the much more well known structured programming language to come out of the Bell System, I've got some burning curiosity about what EPLX might have looked like, how it compared with C, if there would've been any chance of it being generalized for routine software development, or if it was still incredibly particular to switching and thus not really a candidate for anything other than switching code for 1A processors.  The intro of the paper linked above implies the control flow structures may have been influenced by Pascal, but I have not yet pursued a full version of that paper to further determine specifics.