emails:comets@math.jussieu.fr,nobuo@math.kyoto-u.ac.jp. 
URLs:http://www.proba.jussieu.fr/pageperso/comets/comets.html, 
http://www.math.kyoto-u.ac.jp/~nobuo 
AMS-Code:60K35,60G42, 82A51, 82D30