Marco Ajmone Marsan Gabriele Ginella Roberta Maglione Michela Meo Performance analysis of hierarchical cellular networks with generally distributed call holding times and dwell times. 248-257 2004 3 IEEE Transactions on Wireless Communications 1 http://dx.doi.org/10.1109/TWC.2003.821154 db/journals/twc/twc3.html#MarsanGMM04