R. Freund:
"P Systems: from Anti-Matter to Anti-Rules";
in: "Proceedings of Seventeenth Brainstorming Week on Membrane Computing", Artes Gr a cas Moreno, S.L., sevilla, 2019, 978-84-14347-4, 41 - 58.
https://publik.tuwien.ac.at/files/publik_285669.pdf