F. Radicchi, S. Fortunato and A. Vespignani.
in A. Scharnhorst et al. (eds) Models of Science Dynamics, pp 233-257, Springer-Verlag, Berlin Heidelberg 2012.
in A. Scharnhorst et al. (eds) Models of Science Dynamics, pp 233-257, Springer-Verlag, Berlin Heidelberg 2012.