1. John J. O'Conner and Edmund F. Robertson. "Wallace John Eckert" in The MacTutor History of Mathematics Archive   (University of St. Andrews Scotland, School of Mathematics and Statistics, http://turnbull.dcs.st-and.ac.uk/history/Mathematicians/Eckert_Wallace.html, 2003 October 15, archived for reference http://www.dgatx.com/computing/people/John-OConner/pubs/2003/Wallace-Eckert/Eckert_Wallace.html, 2003 October 15)