[Retros] Issue of co-authorship

[afretro]

Dear Nicolas and all,
It was good to see the ⌠theme summary.■
As I understand, problems appearing on the Retro Mailing List are considered to have been published thereby. In some cases, however, the question of co-authorship arises. I will use an analogy from the realm of orthodox composition to highlight the controversy of this point.
Let▓s suppose composer X has published a moremover in N moves. Then composer Y publishes a moremover in N-1 moves showing a very similar (or identical) idea. In that case, the authorship of the latter problem will be indicated as ⌠Y after X,■ ⌠X, version by Y,■ or even ⌠Y & X.■ In case of record-hunt in the domain of SPGs, however, this approach tends to be neglected. I don▓t mind if the retro society doesn▓t mind either, but this point has got to be made clear.
The reason why I am raising this question is as follows. Yesterday I accidentally met Mr. Reytsen in the street and told him about the Retro Mailing List success of his (again, not mine) idea. He expressed enthusiasm about it and said he would like to quote the ultimate records in the magazine The Problemist of Ukraine. That▓s where the issue of co-authorship comes into play.
Any ideas in this connection, friends?
Best,
Andrey