Sangeeta Bhattacharya Chien-Liang Fok Chenyang Lu Gruia-Catalin Roman MLDS: A flexible location directory service for tiered sensor networks. 1160-1172 2008 31 Computer Communications 6 http://dx.doi.org/10.1016/j.comcom.2008.01.036 db/journals/comcom/comcom31.html#BhattacharyaFLR08