George Howard is on best behaviour at http://cosmictusk.com/live-link-comet-and-asteroid-impacts-and-human-soc… … as he provides a link to the full pdf of a very expensive book to buy on Amazon. Go to link above and click on Han Rickman and you will get a list of publications – the pdf is three or so short of the top. The book is by Peter Bobrowsky and Han Rickman, Comet/Asteroid Impact and Human Society, and a must to add to your computer saving library.
See also the next post at http://cosmictusk.com/comet-c2013-a1-mars-impact-sliding-spring/ … which mentions Dr Velikovsky and provides a link to various sites including Ian Tresman's web site. See also http://tallbloke.wordpress.com/2013/02/27/comet-c2013-could-hit-or-miss-…