Well I’m only at the initial stages of “learning” coarrays, and the only sources I have so far are the ones suggested by posters in this thread, which I am still working my way through. I was able to look at the Numrich book suggested by @FortranFan online via LANL. It gives a decent basic intro, but probably a majority of the material deals with implementation details of how to parallel decompose a problem, which is independent of coarrays, and only slips in coarrays as the last piece. I’ll add the papers you found to my list. If I find something I find particularly useful I’ll be sure to post about it here.
A tutorial that I think would be very helpful which I didn’t find, is a nuts-and-bolts “Getting started with coarrays”, which is concerned solely with how to compile and run a coarray program, including installation of additional software, if any, beyond the basic compiler. OpenCoarrays has done a nice job for gfortran, but I’m thinking of a comprehensive one-stop tutorial that covers all compilers. Things vary significantly between compilers; I found Intel to be particularly obtuse. Portability is a key thing when I am considering using a new feature, so from the outset I needed to be able to run my learning examples on multiple platforms (Intel, gfortran, and NAG so far).