The Theropod Archives homepage, where this image originates, begins its story with this welcome:
Welcome to The Theropod Archives, an online registry of theropod-related articles collected in PDF format. The design for this site borrows heavily from Ken Carpenter’s Ankylosaur PDF Library, and in fact it was Ken himself who encouraged me to undertake a similar project for theropod dinosaurs. Following his lead, I have limited the PDF offerings here to works that have been in the literature for 50 years or more. However, I have gone perhaps a step further in furnishing external links to PDFs of newer works (< 50 years) that can be downloaded freely – if, and only if, it appears said works are made available legally. . . .
From a post in Laelaps headlined “The theropods have been released,” via the Public Library of Science blog. The latter comments:
In discussions of Open Access, we always focus on brand new papers and how to make them freely available for readers around the world as well as for people who want to mine and reanalyse the data using robots. But we almost never discuss the need to make the old stuff available. Yet we often lament that nobody reads or cites anything older than five years. . . .