If you’re into history of logic (or mathematics generally), or are just looking for old articles, and you’re stuck at a university whose libraries holdings go back to only about 1965, what can you do? Say you’re looking for a paper from Mathematische Annalen 1924, where do you go to find it online? Well, JSTOR is one option, although not for the Annalen. There you can find back issue of the main English-language journals (Am. J. Math, etc.) including the Journal of Symbolic Logic and various philosophy journals. There are, however, a number of free digitization repositories around the world that have materials in other languages as well. The GDZ has digitized back issues of not just Mathematische Annalen and Mathematische Zeitschrift but also more obscure periodicals such as the Abhandlungen der Gesellschaft der Wissenschaften in Göttingen, Mathematisch-Physikalische Klasse. It’s a little difficult to navigate, especially because in “browse” mode you don’t get the journal titles unless you also select “group by title.” I recommend advanced search with “*” in the title field and “Mathematica” selected in the “Digital Collections” field. There’s a nice list of other such “retrodigitization” repositories, at World Digital Mathematics Library, and an even more extensive and detailed one maintained by Ulf Rehmann here. Most of these repositories also have digitized books (e.g., the GDZ has the collected works of Dedekind and Hilbert). The neatest thing, though, is something I found out a little while ago. The Jahrbuch über die Fortschritte der Mathematik, which was the review journal at the time it was published (1868-1942), is now available as a searchable database. And some of the entries are directly linked to the GDZ and other repositories.