Warren, Truly great stuff! Maybe you should, on top of it all, tell the alien how we "validate" these methods. Richard Prince [log in to unmask] ------------------ The PMFList (http://microbiol.org/PMFList_info.htm) is operated from The Microbiology Network (http://microbiol.org) and supported by our sponsors (http://microbiol.org/sponsor.htm) as a service to the scientific community.