Article date: Nov 1976
Article title: In which DM (Dr. Matrix) is revealed as the guru of PM (Pentagonal Meditation)
Mathematical Games column? Y
Book: 4. The Magic Numbers of Dr. Matrix
Chapter: 19. Calcutta
This data confirmed? yes
Notes
Peter Rowlett (5 September 2022):
Peter Rowlett initial guess (Uncertain)
Peter Rowlett (29 October 2023):
I have seen this chapter and column side-by-side and they match.