At 06:44 PM 7/8/01 +0200, you wrote: >If anybody knows of any studies that >have been done or has any of their own data I'd be very interested. You should absolutely take a look at CiteSeer: http://citeseer.nj.nec.com/cs There's always tons of interesting stuff in there. Or, you could also try the old pfd search: http://searchpdf.adobe.com/