"there exist no grounds whatever, conclusive or inconclusive, for anything that we know"[http://intl.sciencemag.org/cgi/content/full/284/5420/1625]
+
"there exist no grounds whatever, conclusive or inconclusive, for anything that we know"<ref>[http://intl.sciencemag.org/cgi/content/full/284/5420/1625]</ref>