Oliver Berthold Andreas Pfitzmann Ronny Standtke The Disadvantages of Free MIX Routes and how to Overcome Them. 30-45 2000 conf/diau/2000 Workshop on Design Issues in Anonymity and Unobservability http://dx.doi.org/10.1007/3-540-44702-4_3 db/conf/diau/diau2000.html#BertholdPS00