Bjarne Jessen, Daniel Moldt. Some Simple Extensions of Petri's Cycloids. In Michael Köhler-Bußmeier, Ekkart Kindler, Heiko Rölke, editors, Proceedings of the International Workshop on Petri Nets and Software Engineering co-located with 41st International Conference on Application and Theory of Petri Nets and Concurrency (PETRI NETS 2020), Paris, France, June 24, 2020 (due to COVID-19: virtual conference). Volume 2651 of CEUR Workshop Proceedings, pages 194-213, CEUR-WS.org, 2020. [doi]