So this question is heavily related to the questions here and here. Specifically I would like to know if any academics out there (especially in the fields of Maths, Physics, and Engineering) know of good resources for old papers/journal articles. Most of the papers of interest to me are in German and are between the years 1900 and 1930. A lot of these journals do not exist anymore or were renamed. So, it's almost impossible to track down who holds copies of them. Is there a resource/library that specialises in these old articles/texts? Or am I better off just using the suggestions posted in the two linked questions?
Note: I am not specifically interested in finding, say, digital versions of the old papers. I am more interested in knowing if there is a way to find these old papers myself before asking a librarian or asking for an interlibrary loan.