My name turns out to be involved in another case of problematic bibliographic reference, but in contrast with the previous case, I am completely blameless. The book *Mathematical Constants* turns out to contain, as Added in Press, the statement that the “probability” that two integers belonging to the ring * Z[j]* (where

*j*is a primiteve root of unity of order 3) are coprime is equal to

where

(probability is in the usual not-quite-strictly-correct sense of looking at the limit of the proportion in larger and larger balls or boxes centered at 0). For this, a reference is given to a putative unpublished note of mine entitled *“Coprimality and squarefreeness within quadratic fields”. *

However, this note does not exist, and never did! The only reason for this (somewhat casual) claim is that I had explained how to prove this (it is really an exercise, in line with this one) on the NMBRTHRY mailing list back in 2003.