For a clear, textbook treatment of these topics at the introductory (i.e., advanced undergrad or beginning graduate) level, it's hard to beat Benjamin Pierce's "Types and Programming Languages" (MIT Press, 2002). Chapters 20 and 21 cover the basics of recursive types including iso/equi-recursive types and subtyping. And the "Notes" section at the end has lots of references to a bunch of "founding papers" -- at least, as of 20 years ago.

-N

On Tue, Aug 30, 2022 at 1:01 PM Aaron Gray <aaronngray.lists@gmail.com> wrote:

On Tue, 30 Aug 2022 at 17:46, Andreas Rossberg <rossberg@mpi-sws.org> wrote:
>
> Hi François,
>> I’m curious why you would categorise iso-recursive types as nominal. I have always considered them structural as well, since two structurally matching iso-recursive type expressions are still deemed equivalent. That matters in so far as it makes them modular in a way that true nominal types are not.
>
> Iso-recursive types would only behave like nominal in the degenerate case where all type definitions occurring in the entire program (across module boundaries) are tied into a single grand iso-recursive knot, I think.

Are there any founding papers or books on isorecursive and
equirecursive typing ?

Aaron