HP-50g: help remembering library with Interval Arithmetic

[johnb]

Hello again, everyone.

I need help from the hive mind here: I've forgotten exactly where to find a certain library for the HP-50g. The sad thing is, it was recommended to me by someone when we were discussing my similar library on the HP-48g, and I cannot find the thread!

Shame on me.

What I do recall:
(1) It was a library specifically for the 50g, and it included operations for Interval Arithmetic... but that was not the library's primary purpose.
(2) It wasn't in the Museum's archives, it was in some other popular HP-calc archive on the web.
(3) It was written by someone whose credentials would provide adequate reason to expect that their implementation was correct, even for most edge or corner cases. Maybe he was a mathematician... or an electrical or mechanical engineer? (I do recall the author was male. I'm a big supporter of Women-in-STEM so I take positive notice of their work.)

Any clues which library I'm referring to here?