The 'Chess Panorama' excerpt mentions the book 'Spassky's 100 Best Games' by Bruce Cafferty. That should of course be Bernard Cafferty, who also mentioned other last round incidents of the same genre. I'll cover those in another post.
In fact, the 'Chess Panorama' excerpt is from the Foreword to Cafferty's book, written by Leonard Barden. Here's the full text around the excerpt (p.19).
For the moves of the Stein - Spassky game, see Leonid Stein vs Boris Spassky; USSR Championship (1961), Moscow URS (chessgames.com). For the moves of the other two games mentioned above, also from Chessgames.com, see Rodolfo Tan Cardoso vs David Bronstein; Portoroz Interzonal (1958), Portoroz SLO, and Oscar Quinones Carrillo vs Leonid Stein; Amsterdam Interzonal (1964), Amsterdam NED.