\ References
http://protsci.highwire.org/cgi/reprint/11/3/636
http://www.scopus.com/scopus/record/display.url?eid=2-s2.0-0028990098&view=basic&origin=inward&txGid=DZFMxFtNMFSBvMSQaTdX6YH%3a2 and