Guilherme Sperb Machado, Thomas Bocek, Alexander Filitz, Burkhard Stiller: Measuring Interactivity and Geographical Closeness of Online Social Network Users in Support of Social Recommendation Systems; 10th International Conference on Network and Service Management (CNSM 2014), Rio de Janerio, Brazil, November 2014, ISBN 978-3-901882-67-8, pp 187-192. URL: http://publication.pics.mu/papers/Measuring_OSN_Interactivity_and_GeoCloseness_CNSM2014.pdf.