Analysis and visualization of large networks with program package Pajek

Pajek is a program package for analysis and visualization of large networks (networks containing up to one billion of vertices, there is no limit-except the memory size-on the number of lines). It has been available for 20 years. The program, documentation and supporting material can be downloaded and used for free for noncommercial use from its web page: http://mrvar.fdv.uni-lj.si/pajek/.