All I can remember is that it was very high-level / abstact and kind of philosophical, explaining (the discovery or interdependence of) small world networks. I assume that it was +50 years old and 'might' be an iconic paper, but maybe not - surely it was by far not as popular as the, already mentioned, paper "small world networks and their dynamics" by Duncan J. Watts & Steven H. Strogatz, but also it was on a completely different level of math.
I think I found it once on Azimuth Blog from John Carlos Baez. But it is very large and I don't even find "small world network" in the search (it might have also been mentioned by someone in the comment section).