Here, a digital repository of classical and hard-to-find texts including logic diagrams is to be created. Currently, you can use the repository that was created with the free and open-source reference management software Zotero:

At the moment, the Zotero database contains eight subsections, the first four of which cover the periods before and after Euler and Venn. The main focus of the digital repository is on texts with logic diagrams, which have a family resemblance with Euler and Venn diagrams and were created between 1550 and 1880. In principle, however, texts of all periods are recorded. The other four sub-sections relate to texts with logic diagrams in general (for example squares of opposition, pons asinorum, rare or special tree diagrams) as well as research information on points A-D.
Researchers are welcome to fill missing links in the database. Please contact us by e-mail (cf. Impressum) or simply become a member of the zotero group.