Quanbin Chen Min Gao Jian Ma Dian Zhang Lionel M. Ni Yunhao Liu MOCUS: moving object counting using ultrasonic sensor networks. 55-65 2008 3 IJSNet 1 http://dx.doi.org/10.1504/IJSNET.2008.016462 db/journals/ijsnet/ijsnet3.html#ChenGMZNL08