R. Freund, A. Alhazov, S. Ivanov:
"One-Membrane P Systems with Activation and Blocking of Rules.";
in: "Sixteenth Brainstorming Week on Membrane Computing", Gh. Paun et al. (ed.); Fénix Editora, Sevilla, 2018, 23 - 38.
https://publik.tuwien.ac.at/files/publik_276097.pdf