A. Alhazov, R. Freund, Y. Rogozhin:
"Computational Power of Symport/Antiport: History, Advances, and Open Problems";
in: "Membrane Computing · 6th International Workshop, WMC 2005, Vienna, Austria, July 18-21, 2005, Revised Selected and Invited Papers", R. Freund, Gh. Paun, G. Rozenberg, A. Salomaa (ed.); Springer LNCS 3850, Berlin, 2006, (invited), ISBN: 978-3-540-30948-2, 1 - 31.