Emiran Curtmola Alin Deutsch Dionysios Logothetis K. K. Ramakrishnan Divesh Srivastava Ken Yocum XTreeNet: democratic community search. 1448-1451 2008 1 PVLDB 2 http://www.vldb.org/pvldb/1/1454197.pdf db/journals/pvldb/pvldb1.html#CurtmolaDLRSY08