http://www.springerlink.com/content/p1027164r403288u/fulltext.pdf It would make for more interesting discussion (IMHO), if links to full studies were provided when possible. deknow *********************************************** The BEE-L mailing list is powered by L-Soft's renowned LISTSERV(R) list management software. For more information, go to: http://www.lsoft.com/LISTSERV-powered.html Guidelines for posting to BEE-L can be found at: http://honeybeeworld.com/bee-l/guidelines.htm