Kind of tangential but the article talks about VisiCalc, Lotus 1-2-3, and Excel but somehow fails to mention Microsoft's Multiplan (https://en.wikipedia.org/wiki/Multiplan) which was released the year before Lotus 1-2-3 came out. Granted, it wasn't that popular or successful, but it shows that, contrary to what some seem to think, Microsoft was contending in the spreadsheet arena long, long before Excel was even a glimmer on the horizon.