Biswajit Panja Sanjay Kumar Madria Bharat K. Bhargava Energy-Efficient Group Key Management Protocols for Hierarchical Sensor Networks. 201-223 2007 3 IJDSN 2 http://dx.doi.org/10.1080/15501320701205225 db/journals/ijdsn/ijdsn3.html#PanjaMB07