I greatly appreciate constructive feedback, and welcome any comments, reporting of factual errors or broken links, requests for further detail and, especially, offers of additional information. Spam is an awful problem so, in a naïve attempt to beat the dreaded Spambots, I've inserted the word MACH in my e-mail address, below. Simply remove these letters before e-mailing me. Thanks! (Don't forget to remove the "MACH"...)