Characterization of online groups along space, time, and social dimensionsDavid Martin-Borregon, Luca Maria Aiello, Przemyslaw Grabowicz, Alejandro Jaimes and Ricardo Baeza-YatesEPJ Data Sci., 3 1 (2014) 8DOI: https://doi.org/10.1140/epjds/s13688-014-0008-y