Friends: Here is a short paper I wrote some months ago on an invitation from the editor of AJoB. I thought some of you might find you interesting. http://dst.sciencecentral.in/36/3/UAJB_A_1366194-Postprint.pdf Regards. Arun http://orcid.org/0000-0002-4398-4658 http://www.researcherid.com/rid/B-9925-2009 -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.