John L. Pfaltz. A Category of "Undirected Graphs" - A Tribute to Hartmut Ehrig. In Reiko Heckel, Gabriele Taentzer, editors, Graph Transformation, Specifications, and Nets - In Memory of Hartmut Ehrig. Volume 10800 of Lecture Notes in Computer Science, pages 223-230, Springer, 2018. [doi]
Abstract is missing.