R. Freund, A. Alhazov, S. Ivanov:
"Beyond Generalized Multiplicities: Register Machines over Groups";
in: "Seventeenth Brainstorming Week on Membrane Computing Sevilla, February 5 - 8, 2019", Artes Gr a cas Moreno, S.L., 2019, 978-84-14347-4, 1 - 28.