Geometric and analytic properties in the behavior of random walks on nilpotent covering
graphs / by Satoshi Ishiwata, 2004
Internet, http://read.jst.go.jp/public/cs_ksh_008EventAction.do?action4=event&lang_act4=E&judge_act4=2&knkysh_name_code=1000365649,
2009-07-17
Internet, http://www.math.tsukuba.ac.jp/~ishiwata/index-e.html, 2009-07-17