Stephane Durocher Krishnam Raju Jampani Anna Lubiw Lata Narayanan Modelling gateway placement in wireless networks: geometric k-centres of unit disc graphs. 79-86 2008 DIALM-POMC http://doi.acm.org/10.1145/1400863.1400879 conf/dialm/2008 db/conf/dialm/dialm2008.html#DurocherJLN08