Qing Zhang Zhipeng Xie Weiwei Sun Baile Shi Tree Structure Based Data Gathering for Maximum Lifetime in Wireless Sensor Networks. 513-522 http://springerlink.metapress.com/openurl.asp?genre=article&issn=0302-9743&volume=3399&spage=513 2005 conf/apweb/2005 APWeb db/conf/apweb/apweb2005.html#ZhangXSS05