OpenAtlas

Thank you for this interesting question. You already mentioned it and as far as I remember, the reference of a reference ... issue was the exact reason we didn't implemented it.
Because OpenAtlas is already very complex we try to code as generic as possible and in this case, I'm not sure if it's easy implemented or leads us down the rabbit hole.

Before looking into that from a technical perspective I would kindly ask Stefan about his opinion from the model perspective. Does linking references to reference systems make sense and could it be useful in the wider context?
Because my understanding so far is that if you have a lot of references you use an external reference system like e.g. Wikidata but if you have only one or two you use an external reference.
I also don't understand why, in the given example, the external reference link to the entry can't be just replaced with a link to e.g. a Zotero external reference system. But maybe I missed something and would like to leave this for you two to discuss.

For now I turned this into a question but if Stefan decides it to be useful, we can turn it into an issue again.

Thank you for the explanations. Using e.g. BibTeX sounds like a good way to go about it.
I assign this question back to Enric to further comment or closing it but both of you (or anyone), feel free to create an issue for implementing functionality for BibTeX.