Critical difference, by Murray Leinster 68686 [Author: Murray Leinster] [Link: https://www.gutenberg.org/6/8/6/8/68686] [Files: 68686-0.txt; 68686-h.htm] Thanks to Greg Weeks, Mary Meehan and the Online Distributed Proofreading Team at http://www.pgdp.net Regards, Jacqueline