Wikipedia is an ongoing endeavor to create a free encyclopedia through an open computer-mediated collaborative effort. How does Wikipedia grow and maintain its coverage? This page contains supporing material relevant to a publication that examines this question. Diomidis Spinellis and Panagiotis Louridas. The collaborative organization of knowledge. Communications of the ACM, 51(8):68–73, August 2008. (doi:10.1145/1378704.1378720) In the above paper, a longitudinal study of Wikipedia's evolution shows that although Wikipedia's scope is increasing, its coverage is not deteriorating. This can be explained by the fact that referring to an non-existing entry typically leads to the establishment of an article for it. Wikipedia's evolution also demonstrates the creation of a large real world scale-free graph through a combination of incremental growth and preferential attachment. See also the comments appearing in a corresponding blog entry and an update containing an analysis of two more years (2006-2007). The source code used to process Wikipedia's XML dump is distributed as open source software.