Giuseppe Anastasi Marco Conti Mario Di Francesco An Analytical Study of Reliable and Energy-Efficient Data Collection in Sparse Sensor Networks with Mobile Relays. 199-215 2009 EWSN http://dx.doi.org/10.1007/978-3-642-00224-3_13 conf/ewsn/2009 db/conf/ewsn/ewsn2009.html#AnastasiCF09