R. Freund, M. Oswald, P. Sosik:
"Reducing the Number of Catalysts Needed in Computationally Universal Systems without Priorities";
Talk: International Workshop on Descriptional Complexity of Formal Systems, Budapest, Hungary; 2003-07-12 - 2003-07-14; in: "5th International Workshop on Descriptional Complexity of Formal Systems", (2003), 102 - 113.