Little, unknown, English or French research journals with good mathematics In this article by Gian-Carlo Rota, you can read:

"I bought a copy of Frederick Riesz' Collected Papers as soon as the
  big thick heavy oversize volume was published. [...] It was clear that
  Riesz' publications were few. What is more surprising is that the
  papers had been published several times. Riesz would publish the first
  rough version of an idea in some obscure Hungarian journal. A few
  years later, he would send a series of notes to the French Academy's
  Comptes Rendus in which the same material was further elaborated. A
  few more years would pass, and he would publish the definitive paper,
  either in French or in English."

This made me wonder if nowadays there are some (printed or online) research journals (in English or French) that are somewhat obscure (note: I don't mean "obscure because their target audience is composed by few specialists") and nevertheless publish good works by good mathematicians.
 A: Functiones et Approximatio, Commentarii Mathematici is off most of the published lists of journals. Nevertheless it is a serious journal for refereed papers in mathematical research, with a 40-year history of continuous publication. Based in Poznan, Poland, it publishes, in English, papers in analysis and number theory. Among the well-known authors whose papers it has featured is Roger Heath-Brown.
A: A starting point might be archive.org with a lot of historical mathematical texts:


*

*Kalkül der abzählenden Geometrie (Schubert)

*Vorlesungen über die Theorie der automorphen Functionen (Fricke+Klein)

*An introduction to the theory of automorphic functions (L Ford)

*etc.


And if you fish around there other resources all over the internet.


*

*Analysis Situs (Poincaré - see link at the bottom)


These are books and you asked for journals, but at least these are open access (no subscriptions).  In some cases you may have to chase the Journal articles from an academic library, but in many cases you don't have to hit the stacks.
