Late last year, I started a thread (https://www.physicsforums.com/threads/historical-paper-dump-sites.780669/#post-4907513) to solicit/compile a list of URLs with open access to historical papers; shortly after, I discovered that several of them weren't as open as they had been...This morning, I found out why: I happened to discover the during "Open access week" (http://en.wikipedia.org/wiki/Open_Access_Week). So -- does anyone have any other (at least partially) open archives to suggest? For my part, in the interim, I've branched into French- and German-language papers, and found a few more that are *actually* open... - http://www.pnas.org/: Proceedings of the National academy of Sciences. Archive of an English-language journal that I'd never heard of, but apparently all open-access, and there are some gems...for example, Weyl's 1929 Gravitation and the Electron. - http://einsteinpapers.press.princeton.edu/: Free online-only access to Princeton's Einstein Collected Papers series; in addition to the originals and English translations of both papers and correspondence, this includes all of their original content (notes, background essays, etc). Obviously only covers those years that have already been released (through 1923). - http://www.digizeitschriften.de/index.php?id=239&L=2 : A ton of German-language journals; Annalen der Physik is a big one; you can also find a ton of papers by e.g. Boltzmann, Planck, Weyl, etc...but searching is a pain (I've had better luck using Google -- e.g. "h. weyl site:digizeitschriften.de") - http://gdz.sub.uni-goettingen.de/en/dms/suche/ : Göttingen university (home of Born's group, among others) digitization project; seems to be a lot of shared content with digizeitschriften, and its interface is clumsier...the same Google search trick helps though. - http://numdam.org/?lang=en : mostly French articles, focusing on math, but there is plenty of physics mixed in...for instance, a ton of Cartan, e.g. his "On the varieties of affine connection in general relativity", which lays out the Newton-Cartan theory. See in particular the Annales de l'Institut Henri Poincaire. - http://hal.archives-ouvertes.fr/ (or https://hal.inria.fr ?): again mostly French. The gem I found here was the Journal de Physique et Le Radium (which published e.g. Proca's major works) - http://archive.org/: I left this out last time because everyone knows it, and its coverage is still very spotty. - http://arxiv.org/: Also left out because it focuses on contemporary papers. ... And, for completeness, the sites I listed before (with updates) - http://royalsocietypublishing.org: Not all open, but a good chunk of their papers are (1935 and before?). Searching across multiple journals seems to be problematic...but pretty much everything I've wanted has been from RSPA (http://rspa.royalsocietypublishing.org); [Broken] older stuff (e.g. Maxwell's papers) can be found at http://rstl.royalsocietypublishing.org. - http://oxfordjournals.org: Seems to be more open than Royal Society, but still doesn't seem to be all open; but the Progress in Theoretical Physics archive in particular is great. - http://neo-classical-physics.info: English translations, many from articles that aren't freely available in the original language anywhere I've found. - http://web.ihep.su/owa/dbserv/hw.fulltextlist: Similar to the above, but more limited (and static?) selection. - http://retro.seals.ch/digbib/browse4: mostly French; all of Helvetica Acta (Pauli & his assistants; Stueckelberg, ...) - http://gallica.bnf.fr: Haystack of mostly-French stuff. Gems include: Comptes Rendus of the French academy of sciences, Annalen der Physik (though some crucial years are missing), 1933 Solvay Conference proceedings, surely others. - (That user page at Princeton, which I won't link because the rest of the articles there are password-protected, so the good professor probably meant to protect these as well): Mostly experimental-physics articles, many unavailable elsewhere. - http://www.new1.dli.ernet.in [Broken]: digital library of India: Mostly Indian papers. - http://zfbb.thulb.uni-jena.de: Thuringia university library - digitized journal articles, especially Annalen der Physik - http://e-collection.library.ethz.ch: The ETH library; as far as I can tell, a haystack w/ a few needles. - http://www.fourmilab.ch/etexts/einstein/specrel/www/: Unvetted, but any site that has both Einstein and Kropotkin has to be good. - http://www.trivialanomaly.com: unvetted; found on another thread here. A lot of dead links, but looks promising.