In 1992, the book _Semantic Networks in Artificial Intelligence_ contained about 25 chapters on graph notations for logic. It was also published as a collection of related articles in the journal _Computers and Mathematics with Applications_.
After 20 years (2002), the articles became available for free download, but I just discovered them today. Three of them discuss existential graphs: Don D. Roberts, The existential graphs https://www.sciencedirect.com/science/article/pii/0898122192901274 Robert W. Burch, Valental aspects of Peircean algebraic logic https://www.sciencedirect.com/science/article/pii/0898122192901285 John F. Sowa, Conceptual graphs as a universal knowledge representation https://www.sciencedirect.com/science/article/pii/0898122192901377 But the following article from 2014 is much better than the above: From existential graphs to conceptual graphs http://jfsowa.com/pubs/eg2cg.pdf To view or download any of the other articles, see https://www.sciencedirect.com/journal/computers-and-mathematics-with-applications/vol/23/issue/2 https://www.sciencedirect.com/journal/computers-and-mathematics-with-applications/vol/23/issue/6
----------------------------- PEIRCE-L subscribers: Click on "Reply List" or "Reply All" to REPLY ON PEIRCE-L to this message. PEIRCE-L posts should go to peirce-L@list.iupui.edu . To UNSUBSCRIBE, send a message not to PEIRCE-L but to l...@list.iupui.edu with the line "UNSubscribe PEIRCE-L" in the BODY of the message. More at http://www.cspeirce.com/peirce-l/peirce-l.htm .