> Does anyone have an e-mail address or postal address for Yves Hellegouarch?
Yves Hellegouarch is at the University of Caen; I don't know if he has
an email address, but his address is on his homepage
http://matin.math.unicaen.fr/sdad/data/personnel/hellegou/
> Also: Is there some sort of web-resource that lists such information?
Not yet; here in Germany there's something called MathNet
( http://www.math-net.de/ ) that will help you find information like
that for German mathematicians. It is planned to extend MathNet to
Europe eventually.
In general, a very good source for information on number theorists is
Keith Matthews' number theory web from down under with mirrors in
http://www.dpmms.cam.ac.uk/Number-Theory-Web/web.html (UK)
http://www.math.uga.edu/~ntheory/web.html (US)
as well as in Italy.
Finally, Andrew Odlyzko has an email list for people in computational
number theory at
http://www.research.att.com/~amo/misc/cnt-list
And of course you can always try altavista etc.
franz